C program for Regula Falsi Method

Algorithm Enter two guesses value i.e x1 and x2. [note: guesses must selected in such a way that root of the equation is in between gues...

Algorithm

1. Enter two guesses value i.e x1 and x2. [note: guesses must selected in such a way that root of the equation is in between guesses otherwise program display message to enter guess again]
2. Find f1=f(x1) anf f2=f(x2)
3. if f1f2>0 stop the program
4. else, find x0=x1-(f(x1)f(x2))/(f(x2)-f(x1)) and f0=f(x0)
5. if f1f0<0, x2=x0 and f2=f0
6. else, x1=x0 and f1=f0
7. if modulus of (x2-x1)/x2 is less or equal to error criterian i.e e, then print root and stop
8. else, goto step 4.
9. Exit

Program

#include<conio.h>
#include<stdio.h>
#include<math.h>
#define f(x) x*x-4*x-10
#define e 0.0001
void main()
{
float x0,x1,x2,f0,f1,f2,root;
int i=1;
clrscr();
printf("Regula Falsi Method to find root of equation x^2-4x-10=0\n");
printf("Enter values of x1 and x2\n");
a:printf("x1: ");
scanf("%f",&x1);
printf("x2: ");
scanf("%f",&x2);
f1=f(x1);
f2=f(x2);
if((f1*f2)>0)
{
printf("Enter Again\n");
goto a;
}
else
{
printf("steps\tx0\tf0\tx1\tf(x1)\tx2\tf(x2)\n");
b:x0=x1-((f1*(x2-x1))/(f2-f1));
f0=f(x0);
printf("%d\t%.4f\t%.4f\t%.4f\t%.4f\t%.4f\t%.4f\n",i,x0,f0,x1,f1,x2,f2);
i++;
}
if((f1*f0)<0)
{
x2=x0;
f2=f0;
}
else
{
x1=x0;
f1=f0;
}
if(fabs(f(x0))<=e)
{
root=x0;
printf("The root is %.4f",root);
goto c;
}
else
{
goto b;
}
c:
getch();
}


Output

Note: For other equation you have to change the #define f(x) x*x-4*x-10  as per your requires.