#include

#include

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, );

}

三：使用C语言实现下面三个函数的定积分求解

#define _CRT_SECURE_NO_WARNINGS

#include

#include

#include

//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 ;

}