数值积分之Gauss求积法五点公式

//Gauss求积法五点公式

#include <iostream>

#include <math.h>

using namespace std;

class quadrature

{

private:

int i;

double a, b, f, integral, sum;

double w[5], x[5];

public:

double func(double r)

{

f = 8.168 * r * pow((1 - r / 2.5), 0.17);

return f;

}

void integration();

};

void main()

{

quadrature legendre;

legendre.integration();

}

void quadrature::integration()

{

w[0] = 0.2369269;

w[1] = 0.4786287;

w[2] = 0.5688889;

w[3] = 0.4786287;

w[4] = 0.2369269;

x[0] = -0.90617985;

x[1] = -0.53846931;

x[2] = 0.0;

x[3] = 0.53846931;

x[4] = 0.90617985;

cout << "\n输入下限和上限：";

cin >> a >> b;

sum = 0.0;

for (i = 0; i < 5; i++)

{

sum += w[i] * func((x[i] * (b - a) + b + a) / 2);

}

integral = ((b - a) / 2) * sum;

cout << endl << "积分值 = " << integral << endl;

}