#include <stdio.h>
#include <math.h>
int main()
{
//求0-1的积分值//
double x,y,t,a,b,k;
double result=0;
x=0;
printf("请输入积分上限：k=");
scanf("%f",&k);
t=0.00001;
b=k/t;
for(a=0;a<b;a=a+1)
 {  x=x+t;
    y=x*x+2*x+3;
     result=sin(y)*t+result;
 }
printf("result=%f\n",result);

}
感觉没错，但为什么结果一直是算出来是0

k是double
scanf double 要用 %lf

恩，是的，向大佬低头

#include <stdio.h>
#include <math.h>
int main()
{ 
double x=0,y,t,a,b,k,result=0;
printf("请输入积分上限：k=");
scanf("%lf",&k);
t=0.00001;
b=k/t;
for(a=0;a<b;a=a+1)
  {  x=x+t; 
     y=x*x+2*x+3;
     result=sin(y)*t+result;
  }

 printf("result=%lf\n",result);
}