Secant Method

#include <stdio.h>
#include <math.h>
double f(double x)
{
    return pow(x,2)-4*x-10; //Given equation may will be changed
}
int main()
{
    float x1,x2,x3,f1,f2,E;
    printf("Enter initial points X1 and X2: ");
    scanf("%f %f",&x2,&x3);
    printf("Enter the tolerance value: ");
    scanf("%f",&E);

    do
    {
        x1 = x2;
        x2 = x3;

        f1 = f(x1);
        f2 = f(x2);

        x3 = (f2*x1 - f1*x2)/(f2-f1);
    }
    while(fabs((x3-x2)/x3)>E);
    printf("Root is: %.2f\n",x3);

    return 0;
}

//Reference : Nemerical Methods by E Balagurusamy (2016-2017) pages (153 -154)