FalsePosition.cpp

#include <iostream>
#include <iomanip>
#include <math.h>


#define f(x) x*x-x-2

using namespace std;

int main()
{
    float x0, x1, x, f0, f1, f, e;
    int step = 1;

    cout << setprecision(6) << fixed;

up:
    cout << "Enter first guess: ";
    cin >> x0;
    cout << "Enter second guess: ";
    cin >> x1;
    cout << "Enter tolerable error: ";
    cin >> e;

    f0 = f(x0);
    f1 = f(x1);

    if (f0 * f1 > 0.0)
    {
        cout << "Incorrect Initial Guesses." << endl;
        goto up;
    }
    cout << endl
         << "*********************" << endl;
    cout << "False Position Method" << endl;
    cout << "*********************" << endl;
    do
    {
        x = x0 - (x0 - x1) * f0 / (f0 - f1);
        f = f(x);

        cout << "Iteration-" << step << ":\t x = " << setw(10) << x << " and f(x) = " << setw(10) << f(x) << endl;

        if (f0 * f < 0)
        {
            x1 = x;
            f1 = f;
        }
        else
        {
            x0 = x;
            f0 = f;
        }
        step = step + 1;
    } while (fabs(f) > e);

    cout << endl
         << "Root is: " << x << endl;

    return 0;
}