#include<iostream>

#include<math.h>

using namespace std;

int main(){

    float fun(float x);

    float a, b;

    cout << "请输入函数X^2的定积分的下限a和上限b：";

    cin >> a >> b;

    int n = ;//将区间划分成50份

    float h = (b - a) / n;//h是每个区间分大小

    float s = ;//s是矩形的面积的和

    float i = ;

    for (i = a; i < b; i += h){

        s = s + fun(i)*h;

    }

    cout << "\n结果是:" << s << endl;

    cout << endl;

}

float fun(float x){

    return pow(x, );

}

#define _CRT_SECURE_NO_WARNINGS

#include <stdio.h>

#include <stdlib.h>

#include <math.h>

//使用矩形法来求定积分的通用函数

//p是函数指针，a是下界，b是上界，n是等分数

float integral(float(*p)(float), float a, float b, int n)

{

    int i;

    float area=;

    float ew = (b - a) / n;

    for (i = ; i <= n;i++)

        area += (*p)(a + i*ew)*ew;

    return area;

}

float f_sin(float x)

{

    return sin(x);

}

float f_cos(float x)

{

    return cos(x);

}

float f_exp(float x)

{

    return exp(x);

}

int main()

{

    float a, b,area;

    float(*p)(float);

    int n = ;

    printf("test sin,input a,b:");

    scanf("%f,%f", &a, &b);

    p = f_sin;

    area = integral(p, a, b, n);

    printf("get value:%f\n", area);

    printf("test cos,input a,b:");

    scanf("%f,%f", &a, &b);

    p = f_cos;

    area = integral(p, a, b, n);

    printf("get value:%f\n", area);

    printf("test exp,input a,b:");

    scanf("%f,%f", &a, &b);

    p = f_exp;

    area = integral(p, a, b, n);

    printf("get value:%f\n", area);

    system("pause");

    return ;

}