第十三周作业 2.0

#include <iostream>
#include<Cmath>  //为便于对比结果，main函数中调用了Cmath中的库函数sin和cos
using namespace std;
const double pi=3.1415926;
double mysin(double);
double mycos(double);
double myabs(double);   //程序中需要求精度的绝对值，也用自定义函数完成吧
int main( )
{
cout<<"sin(π/2)的值为"<<mysin(pi/2)<<endl;
cout<<"cos(87°)的值为"<<mycos((87.0/180)*pi)<<endl;
cout<<"sin(π/2)的更精确的值为"<<sin(pi/2)<<endl;  //库函数提供的值
cout<<"cos(87°)的更精确的值为"<<cos((87.0/180)*pi)<<endl;
return 0;
}
//下面定义mysin函数
double mysin(double x)
{
int n=1,sign=1;
double sum=0,a,b;
a=x;
do
{
b=a/n;
sum+=b*sign;
a*=x*x;
n=n*(n+1)*(n+2);
sign*=(-1);
}while(myabs(b)>=0.00001);
return sum;
}
//下面定义mycos函数
double mycos(double x)
{
int n=2,sign=1;
double sum=1,a,b;
a=x*x;
do
{
b=a/n;
sum-=b*sign;
a*=x*x;
n*=(n+1)*(n+2);
sign*=(-1);
}while(myabs(b)>=0.00001);
return sum;
}
//下面定义myabs函数
double myabs(double x)
{
return(x>0? x:-x);
}