NUmeric : False Position code

 

Sample equation for False position

F(x)=7.50x⁴+8.5x³-11.5x²+12x¹-55.

 

 

//false position

#include<stdio.h>

#include<math.h>

#include<iostream>

using namespace std;

int main()

{

    float xi,xu,xr,Es,a[40],old=0,Ea;

    int n,K=1;

    cout<< "HIghest power in the equation : " ;

    cin>>n;

    //.........................................

    printf("Enter Xi =");

    scanf("%f",&xi);

    printf("Enter Xu =");

    scanf("%f",&xu);

    printf("Enter Es =");

    scanf("%f",&Es);

    //..........................................

     printf("\n");

    printf("enter coefficient :\n");

    for (int i=n; i>=0; i--)

    {

        printf("X^%d =",i);

        scanf("%f",&a[i]);

    }

     printf("\n");

    //...........................................

    while(1)

    {

        float fxi=0,fxu=0,fxr=0;

//

       for (int i=n; i>=0; i--)

        {

             fxi=fxi+a[i]*pow(xi,i);

             fxu=fxu+a[i]*pow(xu,i);

        }

        xr=xu-((fxu*(xi-xu))/(fxi-fxu));

        for (int i=n; i>=0; i--)

        {

            fxr=fxr+a[i]*pow(xr,i);

        }

  printf("\n\n\nSTEP no: %d\n",K);

        printf("Xi   =  %.2f",xi);

        printf("\nfxi  =  %.2f",fxi);

//

        printf("\nXu   =  %.2f",xu);

        printf("\nfxu  =  %.2f",fxu);

//

        printf("\nXr   =  %.2f",xr);

        printf("\nfxr  =  %.2f",fxr);

//

        Ea=((xr-old)/xr)*100;

        old = xr;

        //cout <<" now =" <<old;

        if(Ea<0)

        {

            Ea=Ea*(-1);

        }

        printf("\nEa= %f",Ea);

        if(fxr == 0)

        {

            break ;

        }

        if((fxr*fxu)<0)

        {

            xi=xr;

            printf("\n\n xI = %f\n\n",xi);

        }

        else if ((fxr*fxi)<0)

        {

            xu=xr;

            printf("\n\n Xu =%f\n\n",xu);

        }

        if(Ea<Es)

        {

            break;

        }

        K++;

    }

    return 0;

}