YTU:C语言习题矩形法求定积分

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Description

写一个用矩形法求定积分的通用函数，分别求

（说明: sin,cos,exp已在系统的数学函数库中，程序开头要用#include<cmath>）。

Input

输入求sin(x) 定积分的下限和上限
输入求cos(x) 定积分的下限和上限
输入求exp(x) 定积分的下限和上限

Output

求出sin(x)的定积分
求出cos(x)的定积分
求出exp(x)的定积分

Sample Input

0 10 10 1

Sample Output

The integral of sin(x) is :0.48The integral of cos(x) is :0.83The integral of exp(x) is :1.76

HINT

主函数已给定如下，提交时不需要包含下述主函数

/* C代码 */

int main()

{

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

    float a1,b1,a2,b2,a3,b3,c,(*p)(float);

    float fsin(float);

    float fcos(float);

    float fexp(float);

    int n=20;

    scanf("%f%f",&a1,&b1);

    scanf("%f%f",&a2,&b2);

    scanf("%f%f",&a3,&b3);

    p=fsin;

    c=integral(p,a1,b1,n);

    printf("The integral of sin(x) is :%.2f\n",c);

    p=fcos;

    c=integral(p,a2,b2,n);

    printf("The integral of cos(x) is :%.2f\n",c);

    p=fexp;

    c=integral(p,a3,b3,n);

    printf("The integral of exp(x) is :%.2f\n",c);

    return 0;

}

/* C++代码 */

int main()

{

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

    float a1,b1,a2,b2,a3,b3,c,(*p)(float);

    float fsin(float);

    float fcos(float);

    float fexp(float);

    int n=20;

    cin>>a1>>b1;

    cin>>a2>>b2;

    cin>>a3>>b3;

    cout<<setiosflags(ios::fixed);

    cout<<setprecision(2);

    p=fsin;

    c=integral(p,a1,b1,n);

    cout<<"The integral of sin(x) is :"<<c<<endl;

    p=fcos;

    c=integral(p,a2,b2,n);

    cout<<"The integral of cos(x) is :"<<c<<endl;;

    p=fexp;

    c=integral(p,a3,b3,n);

    cout<<"The integral of exp(x) is :"<<c<<endl;

    return 0;

}

比较容易的一个题，关键是理解矩形法，本题的ac代码是用矩形右边值的函数值作高，用左边无法ac

下面是代码

#include <stdio.h>

#include <math.h>
float integral(float (*p)(float),float a,float b,int n)
{
float i=0,sum=0.0,k=(b-a)/n;
for(i=0;i<n;i++)
{
sum+=(k*(p(a+(i+1)*k)));//就是运用数学矩形的方法一个一个加求出的值是近似值
}
return (sum);
}
float fsin(float a)
{
return sin(a);
}
float fcos(float a)
{
return cos(a);
}
float fexp(float a)
{
return exp(a);
}

int main()
{
float integral(float (*p)(float),float a,float b,int n);
float a1,b1,a2,b2,a3,b3,c,(*p)(float);
float fsin(float);
float fcos(float);
float fexp(float);
int n=20;
scanf("%f%f",&a1,&b1);
scanf("%f%f",&a2,&b2);
scanf("%f%f",&a3,&b3);
p=fsin;
c=integral(p,a1,b1,n);
printf("The integral of sin(x) is :%.2f\n",c);
p=fcos;
c=integral(p,a2,b2,n);
printf("The integral of cos(x) is :%.2f\n",c);
p=fexp;
c=integral(p,a3,b3,n);
printf("The integral of exp(x) is :%.2f\n",c);
return 0;
}

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