割线法求解非线性方程

//用割线法求解非线性方程

#include <iostream>

#include <math.h>

#include <process.h>

using namespace std;

class secant

{

private:

int iteration;

double eps, error, f, x_new, x_old1, x_old2;

public:

secant()

{

iteration = 0;

}

void solution();

double function(double x)

{

f = 1.55 * pow(x, -0.5) - 7.2 * x + 8.1 * x * x - 4 * pow(x, 3) - 1.3;

return f;

}

};

void main()

{

secant nonlinear;

nonlinear.solution();

}

void secant::solution()

{

cout << "\n输入初始估值x0和x1：";

cin >> x_old1 >> x_old2;

cout << "\n输入公差";

cin >> eps;

if (fabs(function(x_old1)) < eps)

{

cout << "\n解是：" << x_old1 << endl;

exit(0);

}

if (fabs(function(x_old2)) < eps)

{

cout << "\n解是：" << x_old2 << endl;

exit(0);

}

do

{

iteration++;

if (x_old1 == x_old2)

{

cout << "\n遇到了错误x(i) = x(i-1)，异常中断..." << endl;

exit(0);

}

x_new = x_old2 - (function(x_old2) * (x_old2 - x_old1)) / (function(x_old2) - function(x_old1));

error = fabs(function(x_new));

x_old1 = x_old2;

x_old2 = x_new;

}while (error >= eps);

cout << "\n解是：" << x_new << endl;

cout << "\n收敛于" << iteration << "次迭代" << endl;

}