作业2 习题2

/*计算和，差，商，积*/
#include<stdio.h>
int main(void)
{

double num1,num2;
char op;
printf("Type in an expression:");
scanf("%lf%c%lf",&num1,&op,&num2);
switch(op){
case'+':
printf("=%.2f\n",num1+num2);
break;
case'-':
printf("=%.2f\n",num1-num2);
break;
case'*':
printf("=%.2f\n",num1*num2);
break;
case'/':
printf("=%.2f\n",num1/num2);
break;        default:
printf("SORRY,sorry\n");
break;
}
return 0;
}

/*输入x,n，计算x^n*/
#include<stdio.h>
int main(void)
{
int i,n;
double sum, x;
printf("enter x,n:");
scanf("%lf%d", &x, &n);
sum= 1;
for(i = 1; i <= n; i++) {
sum= sum * x;
printf("%.2f\n", sum);
}
return 0;
}

/*计算i^2+1/i的和*/
#include <stdio.h>
int main(void)
{
int i,m,n;
double sum;
printf("enter m and n:");
scanf("%d%d",&m,&n);
sum=0;      /*赋予sum的初值为0*/
for(i=m;i<=n;i++){
sum=sum+i*i+1.0/i;
}
printf("sum=%.2f\n",sum);
return 0;
}

/*计算1-2/3+3/5-4/7+5/9-6/11+...的n项之和*/
#include<stdio.h>
#include<math.h>
int main(void)
{
int i,n,fenzi,fenmu,flag;
double item,sum;
printf("enter n:");
scanf("%d",&n);
flag=1;         /*赋予初值*/
fenzi=1;
fenmu=1;
sum=0;
for(i=1;i<=n;i++){
item=1.0*flag*fenzi/fenmu;

sum=sum+item;
fenzi=fenzi+1;
fenmu=fenmu+2;
flag=-flag;
}
printf("sum=%.2f\n",sum);

return 0;

}

/*输出“还款年限-月还款表”*/
#include <stdio.h>
#include <math.h>     /*程序中调用数学函数*/
int main(void)
{
int year;
double loan,money,my,rate;
scanf("%Lf",&loan);
scanf("%Lf",&rate);
printf("enter year money\n");
for(year=5;year<=30;year++){
my=pow(1+rate,12*year);
money=loan*rate*my/(my-1);
printf("year=%d money=%.0f\n",year,money);
}

return 0;
}

/*调用pow函数求幂*/
#include<stdio.h>
#include<math.h>     /*调用数学函数*/
int main(void)
{
int n,i;
double power,sum;

printf("enter n:");
scanf("%d",&n);
sum=0;
for(i=1;i<=n;i++){
power=pow(2,i)；      /*调用幂函数pow(2,i)计算2的i次方*/
sum=sum+power;
}
printf("sum=%.2f\n",sum);
return 0;
}