写一个用矩形法求定积分的通用函数,分别求∫sin(x)dx, ∫cos(x)dx ,∫e^xdx
#define _CRT_SECURE_NO_WARNINGS#include<stdio.h>#include<stdlib.h>#include<math.h>#define N 10000//积分区间划分成等间距的10000格,划分小矩形越多,积分结果越准确double integral_sin(double a, double b) {double sum = 0;for (double i = a; i <= b; i += (1.0 / N)) {sum += sin(i)*(1.0 / N);//sin(i)*(1.0 / N)为每一个小矩形的面积}return sum;}double integral_cos(double a, double b) {double sum = 0;for (double i = a; i <= b; i += (1.0 / N)) {sum += cos(i)*(1.0 / N);}return sum;}double integral_ex(double a, double b) {double sum = 0;for (double i = a; i <= b; i += (1.0 / N)) {sum += exp(i)*(1.0 / N);}return sum;}void main() {double a, b;printf("请分别输入区间[a,b] a的值与b的值\n");scanf("%lf %lf", &a ,&b);printf("sin函数在%f到%f上的积分为%f\n", a, b, integral_sin(a, b));printf("cos函数在%f到%f上的积分为%f\n", a, b, integral_cos(a, b));printf("e^x函数在%f到%f上的积分为%f\n", a, b, integral_ex(a, b));system("pause");}
