binet formula for fibonacci number check

fibo.c

// using binet formula for fibonacci number check
//author jony bepary
#include <stdio.h>
#include <math.h>

int gen_fibo(int n){
    // using binet formula to generate fibonacci number.
    // can use as fibnonacci checker dependency. or generate fibonacci series
    double sqrt_5 = pow(5, .5); // sqrt(5) can be used
    double F_1_minus = ((1-sqrt_5)/2);
    double F_1_plus = ((1+sqrt_5)/2);
    F_1_minus = pow(F_1_minus, n);
    F_1_plus = pow(F_1_plus, n);
    double res = floor((F_1_plus - F_1_minus)/sqrt_5);
    return res;
}

check_fibo(int Fn){

    double sqrt_5 = pow(5, .5);
    // double F_1_minus = ((1-sqrt_5)/2);
    double phi = ((1+sqrt_5)/2);
    double res = (log10(Fn)+log10(sqrt_5))/log10(phi); // generating nth term of fibonnacci series.
    printf("%d\n", Fn);
    if ((int) gen_fibo(floor(res)) == Fn || (int) gen_fibo(ceil(res)) == Fn || Fn == 0)
    // when input/Fn = 0 then res = inf thats why "|| Fn == 0" is included
    {
        printf("It's Fibonacci number\n");
        return 1;
    }else{
        printf("It's  not Fibonacci number\n");
        return 0;
    }
}