#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#define pi 3.14159265358979323846
double f(double x)
{
return sin (x)+cos (x);
}
double juxing(double (*f)(double),double a,double b)
{
double i=1.0/1000000;
double sum=0,x;
for(x=a;x<=b;)
{
sum+=f(x)*i;
x+=i;
}
return sum;
}
double tixing (double(*f)(double),double a,double b)
{
double i=1.0/1000000;
double s=0,x;
for(x=a;x<=b;)
{
s+=((f(x)+f(x+i))/2)*i;
x+=i;
}
return s;
}
main ()
{
char m;
double a=0, b =pi;
printf ("输入1（矩形算法） 或 2（梯形算法）:\n");
m=getchar();
printf("定积分为：\n");
switch (m)
{
case '1':printf ("%lf\n",juxing (f,a,b));break;
case '2':printf ("%lf\n",tixing (f,a,b));break;
}
}