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MathJax basic tutorial and quick reference

2016-03-10 14:52 696 查看
To see how any formula was written in any question or answer, including this one, right-click on the expression it and choose "Show Math As > TeX Commands". (When you do this, the '$' will not display. Make sure you add these. See the next point.)

For inline formulas, enclose the formula in
$...$
. For displayed formulas, use
$$...$$
.


These render differently. For example, type

$\sum_{i=0}^n i^2 = \frac{(n^2+n)(2n+1)}{6}$


to show ∑ni=0i2=(n2+n)(2n+1)6 (which
is inline mode) or type

$$\sum_{i=0}^n i^2 = \frac{(n^2+n)(2n+1)}{6}$$


to shown∑i=0i2=(n2+n)(2n+1)6(which
is display mode).

For Greek letters, use
\alpha
,
\beta
, …,
\omega
: α,β,…ω.
For uppercase, use
\Gamma
,
\Delta
, …,
\Omega
: Γ,Δ,…,Ω.

For superscripts and subscripts, use
^
and
_
. For example,
x_i^2
: x2i.

Groups. Superscripts, subscripts, and other operations apply only to the next “group”. A “group” is either a single symbol, or any formula surrounded by curly braces
{
}
. If you do
10^10
, you will get
a surprise: 1010.
But
10^{10}
gives what you probably wanted: 1010.
Use curly braces to delimit a formula to which a superscript or subscript applies:
x^5^6
is an error;
{x^y}^z
is xyz,
and
x^{y^z}
is xyz.
Observe the difference between
x_i^2
x2i and
x_{i^2}
xi2.

Parentheses Ordinary symbols
()[]
make parentheses and brackets (2+3)[4+4].
Use
\{
and
\}
for curly braces {}.

These do not scale with the formula in between, so if you write
(\frac{\sqrt x}{y^3})
the parentheses will be too small: (√xy3).
Using
\left(
\right)
will make the sizes adjust automatically to the formula they enclose:
\left(\frac{\sqrt x}{y^3}\right)
is (√xy3).

\left
and
\right
apply to all the following sorts of parentheses:
(
and
)
(x),
[
and
]
[x],
\{
and
\}
{x},
|
|x|,
\langle
and
\rangle
⟨x⟩,
\lceil
and
\rceil
⌈x⌉,
and
\lfloor
and
\rfloor
⌊x⌋.
There are also invisible parentheses, denoted by
.
:
\left.\frac12\right\rbrace
is 12}.

Sums and integrals
\sum
and
\int
; the subscript is the lower limit and the superscript is the upper limit, so for example
\sum_1^n
∑n1.
Don't forget
{
}
if the limits are more than a single symbol. For example,
\sum_{i=0}^\infty i^2
is ∑∞i=0i2.
Similarly,
\prod
∏,
\int
∫,
\bigcup
⋃,
\bigcap
⋂,
\iint
∬.

Fractions There are two ways to make these.
\frac ab
applies to the next two groups, and produces ab;
for more complicated numerators and denominators use
{
}
:
\frac{a+1}{b+1}
is a+1b+1.
If the numerator and denominator are complicated, you may prefer
\over
, which splits up the group that it is in:
{a+1\over b+1}
is a+1b+1.

Fonts

Use
\mathbb
or
\Bbb
for "blackboard bold": CHNQRZ.
Use
\mathbf
for boldface: ABCDEFGHIJKLMNOPQRSTUVWXYZ abcdefghijklmnopqrstuvwxyz.
Use
\mathtt
for "typewriter" font: ABCDEFGHIJKLMNOPQRSTUVWXYZ abcdefghijklmnopqrstuvwxyz.
Use
\mathrm
for roman font: ABCDEFGHIJKLMNOPQRSTUVWXYZ abcdefghijklmnopqrstuvwxyz.
Use
\mathsf
for sans-serif font: ABCDEFGHIJKLMNOPQRSTUVWXYZ abcdefghijklmnopqrstuvwxyz.
Use
\mathcal
for "calligraphic" letters: ABCDEFGHIJKLMNOPQRSTUVWXYZ
Use
\mathscr
for script letters: ABCDEFGHIJKLMNOPQRSTUVWXYZ
Use
\mathfrak
for "Fraktur" (old German style) letters: ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz.

Radical signs Use
sqrt
, which adjusts to the size of its argument:
\sqrt{x^3}
√x3;
\sqrt[3]{\frac
xy}
3√xy.
For complicated expressions, consider using
{...}^{1/2}
instead.

Some special functions such as "lim", "sin", "max", "ln", and so on are normally set in roman font instead of italic font. Use
\lim
,
\sin
, etc. to make these:
\sin x
sinx,
not
sin x
sinx.
Use subscripts to attach a notation to
\lim
:
\lim_{x\to 0}
limx→0

There are a very large number of special symbols and notations, too many to list here; see this shorter listing, or this
exhaustive listing. Some of the most common include:

\lt \gt \le \ge \neq
<>≤≥≠.
You can use
\not
to put a slash through almost anything:
\not\lt
≮ but
it often looks bad.
\times \div \pm \mp
×÷±∓.
\cdot
is
a centered dot: x⋅y
\cup \cap \setminus \subset \subseteq \subsetneq \supset \in \notin \emptyset \varnothing
∪∩∖⊂⊆⊊⊃∈∉∅∅
{n+1 \choose 2k}
or
\binom{n+1}{2k}
(n+12k)
\to \rightarrow \leftarrow \Rightarrow \Leftarrow \mapsto
→→←⇒⇐↦
\land \lor \lnot \forall \exists \top \bot \vdash \vDash
∧∨¬∀∃⊤⊥⊢⊨
\star \ast \oplus \circ \bullet
⋆∗⊕∘∙
\approx \sim \simeq \cong \equiv \prec
≈∼≃≅≡≺.
\infty \aleph_0
∞ℵ0
\nabla
\partial
∇∂
\Im
\Re
ℑℜ
For modular equivalence, use
\pmod
like this:
a\equiv b\pmod n
a≡b(modn).
\ldots
is the dots in a1,a2,…,an
\cdots
is
the dots in a1+a2+⋯+an
Some Greek letters have variant forms:
\epsilon \varepsilon
ϵε,
\phi
\varphi
ϕφ,
and others. Script lowercase l is
\ell
ℓ.

Detexify lets you draw a symbol on a web page and then lists the TEX symbols
that seem to resemble it. These are not guaranteed to work in MathJax but are a good place to start. To check that a command is supported, note that MathJax.org maintains a list
of currently supported LATEX commands,
and one can also check Dr. Carol JVF Burns's page of TEX Commands
Available in MathJax.

Spaces MathJax usually decides for itself how to space formulas, using a complex set of rules. Putting extra literal spaces into formulas will not change the amount of space MathJax puts in:
a␣b
and
a␣␣␣␣b
are both ab.
To add more space, use
\,
for a thin space ab;
\;
for
a wider space ab.
\quad
and
\qquad
are
large spaces: ab, ab.

To set plain text, use
\text{…}
: {x∈s∣x is
extra large}.
You can nest
$…$
inside of
\text{…}
.

Accents and diacritical marks Use
\hat
for a single symbol ˆx,
\widehat
for
a larger formula ^xy.
If you make it too wide, it will look silly. Similarly, there are
\bar
ˉx and
\overline
¯xyz,
and
\vec
→x and
\overrightarrow
→xy and
\overleftrightarrow
↔xy.
For dots, as in ddxx˙x=˙x2+x¨x,
use
\dot
and
\ddot
.

Special characters used for MathJax interpreting can be escaped using the
\
character:
\$
$,
\{
{,
\_
_,
etc. If you want
\
itself, you should use
\backslash
∖,
because
\\
is for a new line.

(Tutorial ends here.)

It is important that this note be reasonably short and not suffer from too much bloat. To include more topics, please create short addenda and post them as answers instead of inserting them into this post.

discussion faq mathjax reference
share
edited Feb 19 at 11:07

community wiki

55 revs, 18 users 52%

MJD

12
Some capital Greek letters are the same as the Roman equivalents, so they are not separated in LATEX.
For a capital beta, one must use something like
\mathrm{B}
: B – robjohn♦ Aug
28 '12 at 2:06
36
for a beginner I find this site very helpful – Monkey
D. Luffy Aug 28 '12 at 4:35
110
Thanks for putting this all together! – J. M. Aug
28 '12 at 11:03
3
Two related questions: How do I insert a table when asking a question? and How
to show the integral symbol on this site? – Martin Sleziak Aug
28 '12 at 13:26
2
@Henning When I ranked features in my mind to decide whether to include them,
\varphi
and
\varepsilon
were very close to the threshhold for inclusion. Martin Sleziak has since added
them, which I agree is a good idea. – MJD Aug
28 '12 at 16:33
11
A quick addition to point 11: If you want to use a sin-like
symbol that is not already defined, the command is
\operatorname
: e.g.,
\operatorname{Spec} A
gives SpecA. – Charles
Staats Aug 28 '12 at 16:45
6
It might be useful to mention hanging subscripts for things like
_5C_3
5C3.
You could also mention
\frac
vs
\dfrac
. – axblount Aug
29 '12 at 18:09
3
My basic idea is that if a beginner can express a formula clearly, then someone else can come in and clean up the typesetting afterwards. I am considering getting rid of the section about
\big
,
\left
,
and
\right
for this reason, and trimming the section on spacing. – MJD Aug
30 '12 at 2:06
5
Most of the references to TeX or LaTeX in this and the answers ought to be to MathJaX (the exception that I can see being the output of Detexify). I know this is a bit pedantic, but would it be alright to
correct this? – Loop Space Sep
11 '12 at 14:13
2
@AndrewStacey Thanks for pointing this out. Let's by all means be as correct as possible, particularly when there's no extra cost. – MJD Sep
11 '12 at 14:15
4
@MJD Except that this is meant as a tutorial for those who aren't familiar with the distinction (and there really is a distinction: "slightly incompatible implementations" doesn't really fit the bill here).
One thing tutorials often include is a "Where to find out more" section. This doesn't. Someone who doesn't know the distinction might be tempted to search for help on TeX or LaTeX instead and wonder why it doesn't work. – Loop
Space Sep 11 '12 at 14:40
3
@axblount But that's precisely the wrong way around to think about it! The likelihood is that someone will look at this tutorial to figure out how to write something on the Maths-SX site: i.e., to use MathJaX.
If they can't find help here, where do they go? If they have the idea that MathJaX is "just a javascript implementation of TeX" then they might think to look for help with TeX, but that is quite possibly not going to be helpful. – Loop
Space Sep 11 '12 at 15:08
4
@axblount For a start, you've changed the goalposts: "LaTeX math expressions". LaTeX is so much more than just a way of typesetting maths! Second, I don't really know but it wouldn't take
me long to cook one up. I don't use MathJaX so I haven't explored it. But I know, for example, that it can't handle catcode changes. Which means that I can't make
(
and
)
automatically resizeable. I can in LaTeX. – Loop
Space Sep 11 '12 at 16:04
25
I wish I saw this post when I first joined. This post should be a main link on the home page. There should be a button under each box: NEW TO LATEX, CLICK HERE FOR EXAMPLES. This is extremely useful, concise. – user1527227 May
31 '13 at 18:09
4
@MJD: I use
\mathrm
in many places; e.g. dx in
integrals and derivatives and for operator names that don't need the full force of
\operatorname
.
\mathrm
was intended for roman symbols in math mode;
\text
was intended for text because of the way it spaces things. See this
TEX thread. Since I don't believe we can use preambles in MathJax, we can't use
\DeclareMathOperator
, though we can use
\newcommand
, but that is orthogonal to the use of
\mathrm
vs
\text
for math symbols. – robjohn♦ Jun
10 '13 at 16:23
| show 45 more
comments

25 Answers

active oldest votes

up vote 183down vote

Matrices

Use
$$\begin{matrix}…\end{matrix}$$
In between the
\begin
and
\end
, put the matrix elements. End each matrix row with
\\
, and separate matrix elements with
&
. For example,

$$
\begin{matrix}
1 & x & x^2 \\
1 & y & y^2 \\
1 & z & z^2 \\
\end{matrix}
$$

produces:

1xx21yy21zz2

MathJax will adjust the sizes of the rows and columns so that everything fits.

To add brackets, either use
\left…\right
as in section 6 of the tutorial, or replace
matrix
with
pmatrix
(1234),
bmatrix
[1234],
Bmatrix
{1234},
vmatrix
|1234|,
Vmatrix
∥1234∥.

Use
\cdots
\ddots
vdots
⋮ when
you want to omit some of the entries:

(1a1a21⋯an11a2a22⋯an2⋮⋮⋮⋱⋮1ama2m⋯anm)

For "augmented" matrices, put parentheses or brackets around a suitably-formatted table; see arrays below for details. Here is an example:

[123456]

is produced by:

$$ \left[
\begin{array}{cc|c}
1&2&3\\
4&5&6
\end{array}
\right] $$

The
cc|c
is the crucial part here; it says that there are three centered columns with a vertical bar between the second and third.

For small inline matrices use
\bigl(\begin{smallmatrix} ... \end{smallmatrix}\bigr)
, e.g. (abcd) is
produced by:

$\bigl( \begin{smallmatrix} a & b \\c & d \end{smallmatrix} \bigr)$


share
edited Jul 3 '15 at 18:06




Rory Daulton
24.4k14

answered Aug 28 '12 at 4:17




MJD
38.7k62753

8
This says "End each matrix row with \\". But there is no reason to end the LAST row of the matrix that way. The double backslash means: now go on to the next row. But there isn't any next row after the last
one. – Michael Hardy Aug
28 '14 at 5:15
add a comment |
up vote133 down vote

Aligned equations

Often people want a series of equations where the equals signs are aligned. To get this, use
\begin{align}…\end{align}
. Each line should end with
\\
, and should contain an ampersand at the point to align at, typically immediately
before the equals sign.

For example,

√37=√732−1122=√732122⋅732−1732=√732122√732−1732=7312√1−1732≈7312(1−12⋅732)

is produced by

\begin{align}
\sqrt{37} & = \sqrt{\frac{73^2-1}{12^2}} \\
& = \sqrt{\frac{73^2}{12^2}\cdot\frac{73^2-1}{73^2}} \\
& = \sqrt{\frac{73^2}{12^2}}\sqrt{\frac{73^2-1}{73^2}} \\
& = \frac{73}{12}\sqrt{1 - \frac{1}{73^2}} \\
& \approx \frac{73}{12}\left(1 - \frac{1}{2\cdot73^2}\right)
\end{align}

The usual
$$
marks that delimit the display may be omitted here.

share
edited Apr 22 '15 at 7:36

answered Aug 28 '12 at 4:28




MJD
38.7k62753

2
The AMS's Short Math Guide recommends the
align
environment over
eqnarray
in
LaTeX. In MathJax the spacing seems to be the same , but
align
requires one less ampersand per line. – Rahul Aug
28 '12 at 4:41
2
Thanks. I was not sure whether to discuss that. A detailed argument against
eqnarray
is in this article
. – MJD Aug
28 '12 at 4:51
Would you mind if I changed your example to use
align
then? – Rahul Aug
28 '12 at 5:34
@Rahul: Please go ahead and change anything that seems good to change. This is all CW. – MJD Aug
28 '12 at 5:44
Also, if you think you have a better example, please use it; I used the first one I found. – MJD Aug
28 '12 at 5:49
2
Correct me if I'm wrong, but I don't believe the $$ is necessary before and after the \begin{align}. I've certainly never used it. From experience, the \begin{align} puts you into math-display mode by itself. – TravisJ Apr
21 '15 at 12:24
Thanks, I did not know that. – MJD Apr
22 '15 at 7:37
I sometimes find that one line of this environment is too close to another, making them uncomfortable to read. The interline spacing can be adjusted by using input such as
\\[1ex]
instead of
\\
.
(And of course the
1
can be changed to another value such as
1.5
or
.7
in order to get enough space but not too much.) – David
K Jan 30 at 16:29
add a comment |
up vote 109down vote

Definitions by cases (piecewise functions)

Use
\begin{cases}…\end{cases}
. End each case with a
\\
, and use
&
before parts that should be aligned.

For example, you get this:

f(n)={n/2,if n is
even3n+1,if n is
odd

by writing this:

f(n) =
\begin{cases}
n/2,  & \text{if $n$ is even} \\
3n+1, & \text{if $n$ is odd}
\end{cases}

The brace can be moved to the right:if n is
even:n/2if n is
odd:3n+1}=f(n)

by writing this:

\left.
\begin{array}{l}
\text{if $n$ is even:}&n/2\\
\text{if $n$ is odd:}&3n+1
\end{array}
\right\}
=f(n)

To get a larger vertical space between cases we can use
\\[2ex]
instead of
\\
. For example, you get this:

f(n)={n2,if n is
even3n+1,if n is
odd

by writing this:

f(n) =
\begin{cases}
\frac{n}{2},  & \text{if $n$ is even} \\[2ex]
3n+1, & \text{if $n$ is odd}
\end{cases}

(An ‘ex’ is a length equal to the height of the letter
x
;
2ex
here means the space should be two exes high.)

share
edited Jan 25 at 22:09




MichaelChirico
2,23714

answered Aug 28 '12 at 4:34




MJD
38.7k62753

@MJD Do we have to use the additional instruction
\displaystyle
when the formulas displayed are more complex ? – jibe Jul
1 '14 at 14:43
@jibs
\displaystyle
is enabled automatically in displays, for example between
$$…$$
. You should not ever have to use it. – MJD Jul
1 '14 at 14:50
@jibe In general, the separate cases in this notation should be in text style unless they are very very complex (and then, the
{
notation is just wrong anyways). – yo' Aug
25 '14 at 9:53
add a comment |
up vote105 down vote

Symbols

In general, you have to search in long tables about a specific symbol you're looking for, things like Ψ, δ, ζ, ≥, ⊆ ...
And it turns out that this operation can be frustrating and time consuming, which can cause the buddy to abandon writing the complete LATEX sentence
in his answer, or in some cases, the complete answer itself.

That's why the tool that I will present you in this post was conceived. Basically, it is a LATEX handwritten
symbol recognition. Example in image:



Here is the website: Detexify² No more frustration.

share
answered Oct 14 '13 at 20:15

community wiki

user93957

7
Amazing site!!! – Silent Oct
16 '13 at 3:30
2
Wow. Thanks! This really helped – Siyanda May
5 '14 at 20:59
add a comment |
up vote91down vote

Arrays

It is often easier to read tables formatted in MathJax rather than plain text or a fixed width font. Arrays and tables are created with the
array
environment. Just after
\begin{array}
the format of each column should be listed,
use
c
for a center aligned column,
r
for right aligned,
l
for left aligned and a
|
for a vertical line. Just as with matrices, cells are separated with
&
and rows are broken using
\\
.
A horizontal line spanning the array can be placed before the current line with
\hline
.

For example,nLeftCenterRight10.2411252−1189−83−2020001+10i

$$
\begin{array}{c|lcr}
n & \text{Left} & \text{Center} & \text{Right} \\
\hline
1 & 0.24 & 1 & 125 \\
2 & -1 & 189 & -8 \\
3 & -20 & 2000 & 1+10i
\end{array}
$$

Arrays can be nested to make an array of tables.

For example,min012300000101112012230123max012300123111232222333333Δ012300123110122210133210

As the source for the preceding array is long, please right-click on one of the tables and choose Show Math As ▸ TeX Commands.

share
edited Aug 28 '14 at 5:17

community wiki

8 revs, 6 users 47%

robjohn

3
You'll have to wrap the contents of each cell in
\text
if you don't want allitalics,weird−lookingspacing,an′oddapostrophes. – Rahul Aug
29 '12 at 21:30
@RahulNarain: True. I used words just for illustration, but I guess the example was slightly misleading. If you'd like to modify it please go ahead.– axblount Aug
29 '12 at 22:00
1
Thanks! I like your numeric example better, since the widths of the entries are different enough that the alignment differences are visually clear. – MJD Aug
30 '12 at 1:37
@robjohn how do you use | while typing , i don't find it in my keyboard...... – ABC Mar
28 '13 at 12:05
@exploringnet: on my keyboard, it is the shifted backslash. It may be in different places (or absent) depending on your keyboard. On my mobile device (iPhone), it is in the shifted numerics, to the right
of the backslash. In mathmode,
\vert
gives | and
\mid
gives ∣,
but neither works in the column spec for an array. If you cannot type it on your keyboard, you can alwaays copy and paste it from another document. – robjohn♦ Mar
28 '13 at 17:39
It should perhaps be mentioned, that in nested arrays there seems to be no option to synchronize column-widths and/or row-heights over the top-level. I didn't find a solution such that if two arrays are stacked
vertically one could make their column-widths matching/fit. – Gottfried Helms Aug
26 '13 at 9:16
1
This could also be convenient for some people, althought it destroys the joy of writing tables in LATEX by
hand! – nullgeppetto Jun
3 '14 at 14:18
@Rahul: why did regulars not press developers to enhance HTML formatting instead of doing inconvenient and resource-devouring detours through MathJax? When a table contains (mostly) formulæ, the use of a
formula-formatting engine looks determined. But when one wants just a table, why should it run software with completely different purpose? I once tried to speak about it at meta.SE, but was gagged. – Incnis
Mrsi Dec 3 '14 at 12:11
@IncnisMrsi What kind of pressure could we apply: bribery, threats, kidnapping? A feature request was made, supported by SE communities,
and declined by SE (on technical grounds, as they say). At least we have the MathJax workaround, with all of its flaws: SO and others have nothing. – 404 Dec
3 '14 at 15:55
add a comment |
up vote68 down vote

Fussy spacing issues

These are issues that won't affect the correctness of formulas, but might make them look significantly better or worse. Beginners should feel free to ignore this advice; someone else will correct it for them, or more likely nobody will care.

Don't use
\frac
in exponents or limits of integrals; it looks bad and can be confusing, which is why it is rarely done in professional mathematical typesetting. Write the fraction horizontally, with a slash:

BadBettereiπ2eiπ2eiπ/2∫π2−π2sinxdx∫π/2−π/2sinxdx

The
|
symbol has the wrong spacing when it is used as a divider, for example in set comprehensions. Use
\mid
instead:

BadBetter{x|x2∈Z}{x∣x2∈Z}

For double and triple integrals, don't use
\int\int
or
\int\int\int
. Instead use the special forms
\iint
and
\iiint
:BadBetter∫∫Sf(x)dydx∬Sf(x)dydx∫∫∫Vf(x)dzdydx∭Vf(x)dzdydx

Use
\,
to insert a thin space before differentials; without this TEX will
mash them together:

BadBetter∭Vf(x)dzdydx∭Vf(x)dzdydx

share
edited Jun 4 '13 at 15:47

community wiki

7 revs

MJD

2
I think the first adjusted fraction looks better than the original, but I don't like the second. In any case, this minor spacing imbalance is too peripheral to belong in a basic MathJax tutorial IMO. Too
likely to scare people away rather than make them feel helped. – Henning Makholm Aug
31 '12 at 21:05
1
@Henning Do you mean that the fraction example is too unimportant even to appear in an addendum on fussy spacing, or that the fussy spacing article is too unimportant to appear as an addendum to the tutorial? – MJD Aug
31 '12 at 23:57
1
I was talking specifically about the fraction example. Mostly I'm concerned that somebody will come away thinking, Eeek! Do I have to worry about THAT to use the site? But it's also arguable that
the disclaimer at the top of the answer ought to take care of that. – Henning Makholm Sep
1 '12 at 21:13
1
@MJD I like the less space, but what if we want to list the bounds for multiple integrals? Like if we have say 3 integrals and we have 3 separate bounds for each how would we list each one? Or do we have
to do \int_bound1^bound2\int_bound3^bound4\int_bound5^bound6?? – TheHopefulActuary Nov
19 '12 at 19:45
@Kyle I think that's exactly what you do in that case. – MJD Nov
19 '12 at 20:09
16
Worth nothing you can use
\middle
with | to get it to work with
\left
and
\right
, like
\left\{x\middle | \frac{x^2}{2} \in \mathbb{z}\right\}
: {x|x22∈z} – asmeurer Jun
9 '13 at 22:49
Thanks very much! I wanted to do that, but didn't know how. – MJD Jun
10 '13 at 15:47
add a comment |
up vote 52down vote

Colors

Named colors are browser-dependent; if a browser doesn't know a particular color name, it may render the text as black. The following colors are standard in HTML4 and CSS2 and should be interpreted the same by most browsers:\color{black}{text}text\color{gray}{text}text\color{silver}{text}text\color{white}{text}text\color{maroon}{text}text\color{red}{text}text\color{yellow}{text}text\color{lime}{text}text\color{olive}{text}text\color{green}{text}text\color{teal}{text}text\color{aqua}{text}text\color{blue}{text}text\color{navy}{text}text\color{purple}{text}text\color{fuchsia}{text}text

HTML5 and CSS 3 define an additional 124 color names that will be supported
on many browsers.

Math Stack Exchange's default style uses a light-colored page background, so avoid using light colors for text. Stick to darker colors like maroon, green, blue, and purple, and remember also that 7–10% of men are color-blind and have difficulty distinguishing
red and green.

The color may also have the form
#rgb
where r,g,b are
in the range or
0
9
,
a
f
and represent the intensity of red, green, and blue on a scale of 0–15,
with
a
=10,
b
=11, …
f
=15. For example:

#000text#00Ftext#0F0text#0FFtext#F00text#F0Ftext#FF0text#FFFtext

#000text#005text#00Atext#00Ftext#500text#505text#50Atext#50Ftext#A00text#A05text#A0Atext#A0Ftext#F00text#F05text#F0Atext#F0Ftext#080text#085text#08Atext#08Ftext#580text#585text#58Atext#58Ftext#A80text#A85text#A8Atext#A8Ftext#F80text#F85text#F8Atext#F8Ftext#0F0text#0F5text#0FAtext#0FFtext#5F0text#5F5text#5FAtext#5FFtext#AF0text#AF5text#AFAtext#AFFtext#FF0text#FF5text#FFAtext#FFFtext

You can have a look here for quick reference on colors in HTML.

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edited Aug 11 '14 at 18:54

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6 revs, 3 users 70%

MJD

2
We should add that colors can be used on items other than text, such as variables and operators. The '\color' command applies to the next item: surround anything longer with braces. – Rory
Daulton Feb 21 '15 at 20:30
add a comment |
up vote 52down vote

System of equations

Use
\begin{array}…\end{array}
and
\left\{…\right.
. For example, you get this:

{a1x+b1y+c1z=d1a2x+b2y+c2z=d2a3x+b3y+c3z=d3

by writing this:

$$
\left\{
\begin{array}{c}
a_1x+b_1y+c_1z=d_1 \\
a_2x+b_2y+c_2z=d_2 \\
a_3x+b_3y+c_3z=d_3
\end{array}
\right.
$$


Alternatively we can use
\begin{cases}…\end{cases}
. The same system

{a1x+b1y+c1z=d1a2x+b2y+c2z=d2a3x+b3y+c3z=d3

is produced by the following code

$$\begin{cases}
a_1x+b_1y+c_1z=d_1 \\
a_2x+b_2y+c_2z=d_2 \\
a_3x+b_3y+c_3z=d_3
\end{cases}
$$


To align the
=
signs use
\begin{aligned}...\end{aligned}
and
\left\{…\right.
(see asmeurer's comment){a1x+b1y+c1z=d1+e1a2x+b2y=d2a3x+b3y+c3z=d3

whose code is

$$
\left\{
\begin{aligned}
a_1x+b_1y+c_1z &=d_1+e_1 \\
a_2x+b_2y&=d_2 \\
a_3x+b_3y+c_3z &=d_3
\end{aligned}
\right.
$$


To align the
=
signs and the terms as in{a1x+b1y+c1z=d1+e1a2x+b2y=d2a3x+b3y+c3z=d3

use
array
with
l
(for "align left"; there are also
c
and
r
) parameters

$$
\left\{
\begin{array}{ll}
a_1x+b_1y+c_1z &=d_1+e_1 \\
a_2x+b_2y &=d_2 \\
a_3x+b_3y+c_3z &=d_3
\end{array}
\right.
$$


Vertical space between equations. As explained in Definition by cases to get a larger vertical space between equations we can use
\\[2ex]
instead
of
\\
. The system

{a1x+b1y+c1z=p1q1a2x+b2y+c2z=p2q2a3x+b3y+c3z=p3q3

is generated by the following code

$$\begin{cases} a_1x+b_1y+c_1z=d_1 \\[2ex] a_2x+b_2y+c_2z=d_2 \\[2ex] a_3x+b_3y+c_3z=d_3 \end{cases} $$


in comparison with

{a1x+b1y+c1z=p1q1a2x+b2y+c2z=p2q2a3x+b3y+c3z=p3q3

whose code is

$$\begin{cases} a_1x+b_1y+c_1z=\frac{p_1}{q_1} \\a_2x+b_2y+c_2z=\frac{p_2}{q_2} \\a_3x+b_3y+c_3z=\frac{p_3}{q_3} \end{cases} $$


In response to elect's comment. The following code

$$ \left\{ \begin{array}{l} 0 = c_x-a_{x0}-d_{x0}\dfrac{(c_x-a_{x0})\cdot d_{x0}}{\|d_{x0}\|^2} + c_x-a_{x1}-d_{x1}\dfrac{(c_x-a_{x1})\cdot d_{x1}}{\|d_{x1}\|^2} \\[2ex] 0 = c_y-a_{y0}-d_{y0}\dfrac{(c_y-a_{y0})\cdot d_{y0}}{\|d_{y0}\|^2} + c_y-a_{y1}-d_{y1}\dfrac{(c_y-a_{y1})\cdot
d_{y1}}{\|d_{y1}\|^2} \end{array} \right. $$


produces

{0=cx−ax0−dx0(cx−ax0)⋅dx0∥dx0∥2+cx−ax1−dx1(cx−ax1)⋅dx1∥dx1∥20=cy−ay0−dy0(cy−ay0)⋅dy0∥dy0∥2+cy−ay1−dy1(cy−ay1)⋅dy1∥dy1∥2

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edited Jun 29 '15 at 11:10

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7 revs, 2 users 94%

Américo Tavares

add a comment |
up vote51 down vote

Continued fractions

To make a continued fraction, use
\cfrac
, which works just like
\frac
but typesets the results differently:

x=a0+12a1+22a2+32a3+44a4+⋯

Don't use regular
\frac
or
\over
, or it will look awful:

x=a0+12a1+22a2+32a3+44a4+⋯

You can of course use
\frac
for the compact notation:

x=a0+12a1+22a2+32a3+44a4+⋯

Continued fractions are too big to put inline. Display them with
$$
$$
or use a notation like [a0;a1,a2,a3,…].

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answered Aug 31 '12 at 19:46

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MJD

The RHS of the following continued fractiona1b1+a2b2+a3b3+⋱=a1b1+a2b2+a3b3+…

can be typeset with the \genfrac command '{\genfrac{}{}{}{}{a_1}{b_1}} {\genfrac{}{}{0pt}{}{}{+}} {\genfrac{}{}{}{}{a_2}{b_2}} {\genfrac{}{}{0pt}{}{}{+}} {\genfrac{}{}{}{}{a_3}{b_3}} {\genfrac{}{}{0pt}{}{}{+\dots}}' – Américo
Tavares Sep 17 '12 at 20:39
I wonder if something like 12+34 would
be good enough? It is much simpler. (
\frac12{\vphantom{1}\atop+}\frac34
) – MJD Sep
17 '12 at 22:30
Yes, it is. I didn't mention it because in User’s Guide for the amsmath Package it is written the following: "Note. For technical reasons, using the primitive fraction commands \over, \atop, \above
in a LATEX document is not recommended (see, e.g., amsmath.faq)." – Américo Tavares Sep
17 '12 at 22:44
1
Happily, we are not writing LATEX documents
here. – MJD Sep 17
'12 at 22:44
4
Or write
\underset{j=1}{\overset{\infty}{\LARGE\mathrm K}}\frac{a_j}{b_j}=\cfrac{a_1}{b_1+\cfrac{a_2}{b_2+\cfrac{a_3}{b_3+\ddots}}}
to get∞Kj=1ajbj=a1b1+a2b2+a3b3+⋱.

Américo Tavares Jan
24 '13 at 9:15
1
@AméricoTavares Or use
\mathop
instead of
\overset
and
\underset
:
\mathop{\LARGE\mathrm K}_{i=1}^\infty \frac{a_i}{b_i}
∞Ki=1aibi

AlexR Feb 21 '15 at 20:48
@AlexR It's easier, thanks! – Américo Tavares May
17 '15 at 13:24
@AméricoTavares, Why don't you edit the answer and put this extremely helpful command into there, I think that would be more helpful. – Subhadeep
Dey Jan 24 at 15:44
add a comment |
up vote 49 down vote

Crossing things out

Use
\require{cancel}
in the first formula in your post that requires cancelling; you need it only once per page. Then use:

y+\cancel{x}y+x\cancel{y+x}y+xy+\bcancel{x}y+xy+\xcancel{x}y+xy+\cancelto{0}{x}y+x0\frac{1\cancel9}{\cancel95} = \frac151995=15

Use
\require{enclose}
for the following:

\enclose{horizontalstrike}{x+y}x+y\enclose{verticalstrike}{\frac xy}xy\enclose{updiagonalstrike}{x+y}x+y\enclose{downdiagonalstrike}{x+y}x+y\enclose{horizontalstrike,updiagonalstrike}{x+y}x+y

\enclose
can also produce enclosing boxes, circles, and other notations; see MathML
menclose
documentation
for a complete
list.

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edited Aug 4 '14 at 15:20

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4 revs

MJD

2
Can I use
\enclose{counterstrike}
? :P – Akiva Weinberger Jul
27 '15 at 19:19
1
That sneaky 19/95=1/5.
Nice one! – Darth Geek Dec
8 '15 at 23:57
add a comment |
up vote 38 down vote

Additional decorations

\overline
: ¯A ¯AA ¯AAA

\underline
: B_ BB_ BBB_

\widetilde
: ˜C ~CC ~CCC

\widehat
: ˆD ^DD ^DDD

\fbox
: E EE EEE

\underleftarrow
: F← FF← FFF←

\underrightarrow
: G→ GG→ GGG→

\underleftrightarrow
: H↔ HH↔ HHH↔

\overbrace
: ⏞(n−2)+⏞(n−1)+n+(n+1)+(n+2)

\underbrace
: (n−2)+(n−1)+n+(n+⏟1)+(n+⏟2)

\overbrace
and
\underbrace
accept a superscript or a subscript, respectively, to annotate the brace. For example,
\underbrace{a\cdot a\cdots a}_{b\text{ times}}
isa⋅a⋯a⏟b times

Additional accents

\check
: ˇI

\acute
: ˊJ

\grave
: ˊK

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edited Jun 9 '14 at 5:10

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6 revs, 4 users 71%

Américo Tavares

add a comment |
up vote 38down vote
\implies
(⟹)
is a marginally preferable alternative to
\Rightarrow
(⇒)
for implication.

There's also
\iff
⟺ and
\impliedby
⟸.

\to
(→)
is preferable to
\rightarrow
or
\longrightarrow
for things like f:A→B.
The reverse is
\gets
(←).

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edited Feb 15 at 19:29

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3 revs, 3 users 75%

leonbloy

1
Why is it preferable? – MJD Jul
9 '13 at 20:00
9
implies looks nicer as the arrow is longer and \to is quicker to right (and it's also what you say in your head while typing it). at least that's what I think. – John
Salvatierrez Jul 29 '13 at 13:21
1
Remember the difference between
\to
and
\mapsto
as in T:R→R,x↦x+1 produced
by
T:\mathbb R\to \mathbb R,\; x\mapsto x+1
yo' Aug
25 '14 at 9:57
2
I prefer using
\to
when it appears as part of a larger propositional formula, rather than at the top level, i.e. p∧((q∨r)→s),
because the spacing is similar to that of other binary operators.
\implies
is better for sentence- or clause-level implications, or in displays, i.e.x+2=4−x⟹x=1.

Mario Carneiro Feb
2 '15 at 14:22
add a comment |
up vote37 down vote

Tags & References

For longer calculations (or referring to other post's results) it is convenient to use the tagging/labelling/referencing system. To tag an equation use
\tag{yourtag}
, and if you want to refer to that tag later on, add
\label{somelabel}
right
after the
\tag
. It is not necessary that
yourtag
and
somelabel
are the same, but it usually is more convenient to do so:

$$ a := x^2-y^3 \tag{*}\label{*} $$

a:=x2−y3

In order to refer to an equation, just use
\eqref{somelabel}


$$ a+y^3 \stackrel{\eqref{*}}= x^2 $$

a+y3(*)=x2

or
\ref{somelabel}


Equations are usually referred to as $\eqref{*}$, but you can also use $\ref{*}$.

Equations are usually referred to as (*),
but you can also use *.

As you can see, references are even turned into hyperlinks, which you can use externally as well, e.g. like this. Note that you can also reference labels in other posts as long
as they appear on the same site, which is especially useful when referring to a question with multiple equations, or when commenting on a post.

Due to a bug blocks containing a
\label
will break in preview
, as a
workaround you can put
$\def\label#1{}$
in your post while editing and remove that on submission - unfortunately this means you won't spot misspelled references before submitting... Just don't forget to remove that
\def
again


share
answered Oct 31 '13 at 10:21

community wiki

Tobias Kienzler

3
Also works in comments:
\eqref{*}
yields a clickable (*) – Tobias
Kienzler Oct 31 '13 at 10:22
To enable automatically tagging your queations with incremental numbers, add <script type="text/x-mathjax-config"> MathJax.Hub.Config({TeX: { equationNumbers: {autoNumber: "all"} }}); </script> to your header. – Gerald
Senarclens de Grancy Jan 20 at 20:56
@GeraldSenarclensdeGrancy That would however yield a global numbering on all answers to one question, not per-answer. And it would break the current expectation of by default not having tags despite using
unstarred
\begin{align}
etc.... Though personally I'd agree with this – Tobias Kienzler Jan
21 at 7:19
add a comment |
up vote 36 down vote

Using
\newcommand

I would like to remark that it is possible to define LaTeX commands as you do in your TeX files. I felt so happy when I first discovered it! It's enough to insert something like

$ \newcommand{\SES}[3]{ 0 \to #1 \to #2 \to #3 \to 0 } $

at
the top of your post (remember the dollars!). Then you can just use your commands as you are used to do: in my example typing
$$ \SES{A}{B}{C} $$
will produce the following:

0→A→B→C→0

It's also possible to use plain
\def
:

\def\ses#1#2#3{0 \to #1 \to #2 \to #3 \to 0}

and then
$\ses{A}{B}{C}$
will produce the same output.

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edited Feb 12 '15 at 12:43

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3 revs, 3 users 67%

Abramo

2
Be aware that this affects the entire post, possibly even the frontpage, so it should be used with
great care. – AlexR Feb
21 '15 at 20:55
add a comment |
up vote 34down vote

Commutative diagrams

AMScd diagrams must start with a "require":

$\require{AMScd}$
\begin{CD}
A @>a>> B\\
@V b V V= @VV c V\\
C @>>d> D
\end{CD}

to get this diagram: Aa→Bb↓=↓cC→dD

@>>>
is used for arrow right

@<<<
is used for arrow left

@VVV
is used for arrow down

@AAA
is used for arrow up

@=
is used for horizontal double line

@|
is used for vertical double line

@.
is used for no arrow

Another example:

\begin{CD}
A @>>> B @>{\text{very long label}}>> C \\
@. @AAA @| \\
D @= E @<<< F
\end{CD}

A→Bvery
long label→C↑∥D=E←F

Long labels increase the length of the arrow and in this version also automatically increase corresponding arrows.

$\require{AMScd}$
\begin{CD}
RCOHR'SO_3Na @>{\text{Hydrolysis,$\Delta, Dil.HCl$}}>> (RCOR')+NaCl+SO_2+ H_2O
\end{CD}

RCOHR′SO3NaHydrolysis,Δ,Dil.HCl→(RCOR′)+NaCl+SO2+H2O

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edited Feb 4 at 15:04

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9 revs, 4 users 68%

Lehs

\begin{CD} RCOHR'SO_3Na @>{\text{Hydrolysis,\Delta, Dil.HCl}>> (RCOR')+NaCl+SO_2+ H_2O \end{CD}

Why does this code not give the correct output? – Quark Feb
4 at 10:04
@Quark: The main error was a missing bracket after HCl. – Lehs Feb
4 at 11:38
@Lehs Thanks. That was a silly mistake :| What if I wanted to write something below the arrow? Also, could you suggest some online website to learn MathJax? – Quark Feb
4 at 11:58
@Quark: then you move a > sign: @>>{\text{very long label}}> I learn MathJax from the examples i.e. in this tread. – Lehs Feb
4 at 15:06
@Lehs Why did you rollback my edit...? You removed the formatting from the list, broke again (in Chrome) the example diagram, and reinserted your duplicate example. Why? – Najib
Idrissi Feb 4 at 15:25
@NajibIdrissi: because your edit appeared as a mess in IE. The diagram wasn't even written out. Maybe there is something wrong in your or in my web-program. Now it looks good in IE. – Lehs Feb
4 at 15:44
@NajibIdrissi: Now it also looks good in Chrome for Windows and for Android, plus Safari for Androids. I don't know what the problem is with the current version. – Lehs Feb
4 at 15:56
add a comment |
up vote 33down vote

Big braces

Use
\left
and
\right
to make braces - (round), [square] and {curly} - scale up to be the size of their arguments. Thus

$$
f\left(
\left[
\frac{
1+\left\{x,y\right\}
}{
\left(
\frac{x}{y}+\frac{y}{x}
\right)
\left(u+1\right)
}+a
\right]^{3/2}
\right)
$$

renders asf([1+{x,y}(xy+yx)(u+1)+a]3/2).

Note that curly braces need to be escaped as
\{ \}
.

If you start a big brace with
\left
and then need to match that to a
\right
brace that's on a different line, use the forms
\right.
and
\left.
to make "shadow" braces. Thus,

$$
\begin{aligned}
a=&\left(1+2+3+  \cdots \right. \\
& \cdots+ \left. \infty-2+\infty-1+\infty\right)
\end{aligned}
$$

renders asa=(1+2+3+⋯⋯+∞−2+∞−1+∞).

There is also a
\middle
construct which is useful when one has a mid-expression brace which must also scale up:

$$
\left\langle
q
\middle\|
\frac{\frac{x}{y}}{\frac{u}{v}}
\middle|
p
\right\rangle
$$

renders as⟨q∥xyuv|p⟩.

Note that constructs like
\left\langle
,
\left|
and
\left\|
are also possible.

share
answered Oct 25 '13 at 17:47

community wiki

E.P.

Note:
\Big( ... \Big)
produces (…) but
this bracket size is fixed in all situations unlike
\left( ... \right)
which varies in size with its contents.
\Big
can be useful in various situations. – Nick Dec
19 '14 at 6:34
add a comment |
up vote28down vote

Arbitrary operators

If an operator is not available as a built-in command, use
\operatorname{…}
. So for things likearsinh(x)

write
\operatorname{arsinh}(x)
since
\arsinh(x)
will give an error and
arsinh(x)
has wrong font and spacing: arsinh(x).

This was already mentioned in a comment by Charles
Staats. You might consider this an addition to the FAQ section on
\lim
,
\sin
and so on.

For operators which need limits above and below the operator, use
\operatorname*{…}
, as inResz=1(1z2−z)=1

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edited Sep 16 '15 at 3:13

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2 revs, 2 users 62%

MvG

We can also use {\rm ...}.
For example, {\rm arsinh} yields arsinh. – Felix
Marin Aug 12 '14 at 0:27
8
@Felix:
\rm
will change the font but not the spacing.
\operatorname{arsinh}x
renders as “arsinhx”
while
{\rm arsinh}x
renders as “arsinhx”.
Notice the added space between operator and operand in the first example, which is missing in the second. On the whole, I'd say that
operatorname
is a lot more in the spirit of semantic markup, declaring what you want to write instead
of how you want to write it, so I'd strongly suggest using this. – MvG Aug
13 '14 at 11:27
3
Thanks. I didn't know there was a difference between them. I always avoided operatorname because
it was too long. – Felix Marin Aug
13 '14 at 14:41
1
Thanks for this. I thought carefully about whether to put
\operatorname
in the main post, and decided to leave it out. The reason is simple: If a beginner omits
\operatorname
, the
resulting formula will still be perfectly clear, and a more experienced user will have no trouble inserting the
\operatorname
where it is needed. So including it in the main post would not be a good use of space. – MJD Aug
16 '14 at 6:28
1
... I always use "\text{operator }". Hmmm, arsinh x vs arsinhx. – Jp
McCarthy Feb 10 '15 at 16:48
If you use the same operator many times, I think you can do
\DeclareMathOperator{\arsinh}{arsinh}
at the post's top. Never tried it though… – MickG Aug
15 '15 at 17:28
add a comment |
up vote26down vote

Limits

To make a limit (like limx→1x2−1x−1),
use this syntax:

First, start off with
$\lim
. This renders as lim.
The backslash is there to prevent things like lim,
where the letters are slanted.

Second, add
\limits_{x \to 1}
inside. The code now looks like
$\lim \limits_{x \to 1}$
, and renders as limx→1.
The
\to
inside makes the right arrow, rendered as →.
The
_
makes the x→1 go
underneath the lim.
Finally, the pair of curly braces
{ }
makes sure that x→1 is
treated as a whole object, and not two separate things.

Lastly, add the function you want to apply the limit to. To make the limit mentioned above, limx→1x2−1x−1,
simply use
$\lim\limits_{x \to 1} \frac{x^2-1}{x-1}$
.

And that is how you make a limit using MathJax.

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edited Jul 17 '14 at 12:25

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2 revs, 2 users 94%

JChau

9
Why not just
\lim_{x\to 1}
limx→1?

As I understand it
\limits
is only needed for operations that don't already understand limits, for example if you want to use
+
and getk+i=1 instead
of +ki=1

When used inline, your suggestion will produce limx→1 instead
of the more compact form limx→1 that
mathjax normally chooses. Are you sure this is good advice? – MJD Feb
26 '14 at 14:10
@MJD
$\lim_{x\to 1}
renders to limx→1,
and
$\lim\limits_{x\to 1
renders as lim\limits_{x\to 1}.
Note how the x→1 is
separated from the first limit, and not directly underneath. We do not write limits like that in real life, so we use
\limits
. – JChau Feb
26 '14 at 16:19
I meant that the second limit renders to limx→1 – JChau Feb
26 '14 at 16:28
6
Limits are usually written that way in typeset materials like papers and books when the limit is inline, rather than a displayed formula, and that's why MathJax typesets it that way. – MJD Feb
26 '14 at 16:41
4
The issue with this answer is that it is trying to "force" display mode on inline code. Doing so makes the text look less pretty. For example, see how the spacing between the lines change when I force display
mode using
\lim\limits_{x\mapsto 1}\dfrac1x
: limx↦11x.
On the other hand, when I let TEX do
what it wants to do, using
\lim_{x\mapsto 1}\frac1x
, the spacing between the lines stays the same, which is much neater: limx↦11x.
This is much easier on the eyes. If you want to make your math mode more prominent then take a new line using
$$-$$
user1729 Jul
17 '14 at 12:30
2
The moral is: TEX was
written by a jolly clever chap. Let it do what it wants, because it does it for a reason! – user1729 Jul
17 '14 at 12:35
Part 11 of the "question" shows how to write limits in the way they were meant to be written in LaTeX and MathJax. – David
K Nov 14 '15 at 23:17
add a comment |
up vote18 down vote

Absolute values and norms

The absolute value of some expression can be denoted as
\lvert x\rvert
or, more generally, as
\left\lvert … \right\rvert
. It renders as ∣x∣.

The norm of a vector (or similar) can be denoted as
\lVert v\rVert
or, more generally, as
\left\lVert … \right\rVert
. It renders as ∥v∥.
(You may also write
\left\|…\right\|
instead.)

In both cases, the rendering is better than what you'd get from
|x|
or
||v||
, which render with bars that don't descend low enough and sub-optimal spacing. At least on some browsers, so here is a screenshot how it looks for me,
using Firefox 31 on OS X:



And here is the same formula rendered by your browser:

|x|,||v||⟶∣x∣,∥v∥

It was typeset as

$$|x|, ||v|| \quad\longrightarrow\quad \lvert x\rvert, \lVert v\rVert$$


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edited Aug 13 '14 at 11:59

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4 revs, 3 users 89%

MvG

4
You can use
\|x\|
instead of
\lVert x \rVert
; ∥x∥ and ∥x∥.
(I don't think that there is a difference between them. I've tried [asking on SE](tex.stackexchange.com/questions/77767/whats-the-correct-way-to-write-norm).) – Martin
Sleziak Jun 24 '14 at 8:48
On my browser
|x|
and
\lvert x\rvert
(|x| and ∣x∣)
look identical, contrary to your claim. Perhaps you need to show an example more complicated than just 'x'? – MJD Jun
24 '14 at 12:39
@MJD: What's your browser? I included a screenshot to support my claim. – MvG Aug
13 '14 at 11:24
Usually various versions of Firefox on either Linux or Windows. I happen to have Windows 8 booted now, so here's a screenshot from there:a.pomf.se/jrujkq.PNG The
bar height looks good on both pairs of symbols; the spacing is a little off for the
||
version. On Linux they looked the same. – MJD Aug
13 '14 at 17:02
Here's a screenshot with FF 31.0 under Linux: a.pomf.se/fhwmjo.pngMJD Aug
16 '14 at 6:23
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up vote 16 down vote

Left and Right Implication Arrows

Another way to display the arrows for right and left implication instead of using

$\Rightarrow$
,
$\Leftarrow$
and
$\Leftrightarrow$


which produces ⇒, ⇐ and ⇔ respectively,
you can use

$\implies$
for ⟹,
$\impliedby$
for ⟸ and
$\iff$
for ⟺

The latter of which produces longer arrows which may be more desirable to some.

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edited May 6 '14 at 22:15

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jnh

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up vote 9 down vote

Long division

$$
\require{enclose}
\begin{array}{r}
13  \\[-3pt]
4 \enclose{longdiv}{52} \\[-3pt]
\underline{4}\phantom{2} \\[-3pt]
12  \\[-3pt]
\underline{12}
\end{array}
$$

134524_1212_

One important trick shown here is the use of
\phantom{2}
to make a blank space that is the same size and shape as the digit
2
just above it.

This is adapted from http://stackoverflow.com/a/22871404/3466415 (which uses slightly different but not less valid formatting).

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edited Jul 27 '15 at 20:19

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5 revs, 3 users 93%

David K

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up vote8down vote
The degree symbol for angles is not
^\circ
. Although many people use this notation, the result looks quite different from the canonical degree symbol shipped
with the font:

90°
renders as 90° while
90^\circ
renders
as 90∘.

If your keyboard doesn't have a ° key, feel free to copy from this post here, or follow these suggestions.

Note that comments below indicate that on some configurations at least,
°
renders inferior to
^\circ
. And I recently had a
post of mine edited just for the sake of turning
°
into
^\circ
, indicating that someone felt rather strongly about this. So the suggestion above does seem somewhat controversial at the moment. I maintain that from a semantic point
of view,
°
is superior to
^\circ
, and if the rendering suffers from this, then it's a bug in MathJax. After all, LaTeX offers a proper degree symbol in the tex companion fonts, indicating that someone there, too, decided that
^\circ
is
not perfect. But if things are broken now, I can't fault people from pragmatically sticking with the rendering they prefer. Personally I prefer semantics, also for the sake of screen readers.

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edited Jul 12 '15 at 6:28

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MvG

If mathjax loads siunitx or gensymb, there is then \degree in latex which is the degree symbol. – dustin Feb
17 '15 at 22:29
@dustin: I couldn't find siunitx or gensymb mentioned anywhere in the MatJax source repository. Are they available as some kind of third-party extension? If so, where? Since MathJax is not LaTeX,
packages can't be loaded unless they have been migrated. By the way, all occurrences of “degree” in the MathJax sources refer to something else, as far as I can tell, so there really doesn't seem to be a
\degree
macro. There should be one, imho. – MvG Feb
17 '15 at 23:39
I am not a mathjax expert. I just know latex. I just gave that suggestion in case they were available. Siunitx would
be a great package to have. If you aren't familiar, you will see the advantage by scanning the documentation on ctan. – dustin Feb
17 '15 at 23:43
7
On my display, ° looks bad and
^\circ
looks good: a.pomf.se/xnlfyg.pngMJD Mar
24 '15 at 21:10
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up vote 8 down vote
To highlight an equation, \bbox can be used. E.g,

$$ \bbox[yellow]
{
e^x=\lim_{n\to\infty} \left( 1+\frac{x}{n} \right)^n
\qquad (1)
}
$$

produces

ex=limn→∞(1+xn)n(1)

or

$$ \bbox[border:2px solid red]
{
e^x=\lim_{n\to\infty} \left( 1+\frac{x}{n} \right)^n
\qquad (2)
}
$$

produces

ex=limn→∞(1+xn)n(2)

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edited Jan 10 at 20:02

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webbertiger

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up vote 8 down vote

Giving reasons on each line of a sequence of equations

To produce this:v+w=0Given−w=−w+0additive
identity−w+0=−w+(v+w)equations (1) and (2)

write this:

\begin{align}
v + w & = 0  &&\text{Given} \tag 1\\
-w & = -w + 0 && \text{additive identity} \tag 2\\
-w + 0 & = -w + (v + w) && \text{equations $(1)$ and $(2)$}
\end{align}


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edited Feb 15 at 18:33

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David K

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up vote 4 down vote

Pack of cards

If you are asking (or answering) a combinatorics question involving packs of cards you can make it look more elegant by using
\spadesuit
,
\heartsuit
,
\diamondsuit
,
\clubsuit
in math mode:♠♡♢♣

Or if you're really fussy:

\color{red}{\heartsuit}
and
\color{red}{\diamondsuit}


♡♢

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edited Feb 1 at 13:10

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David

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