TRIGALGE - Easy Calculation

TRIGALGE - Easy Calculation(link to the question)

to solve equation like A*x + B*sin(x) = C.

do the following steps :

1.  A * x  +  B * sin(x) - C = 0 = (say it) f(x)

2.  Apply Newton - Ralphson (link) approximation.

#include<stdio.h>
#include<math.h>

int main()
{
    int t,six;  double a,b,c,x1,x2;

    scanf("%i",&t);

    while(t--)
    {
        scanf("%lf%lf%lf",&a,&b,&c);

        x1 = -1;

        x2 = c/a;
        
        six = 6;

        while(x2!=x1 && six--)
        {
            x1 = x2;
            x2 = x1 - ( a*x1 + b*sin(x1) - c )/ ( a + b*cos(x1) );
        }

        printf("%lf\n",x2);
    }

    return 0;
}