triangle area calculator, It keeps showing 0, why?

Question

I am making a triangle area calculator, but it only show 0 instead of answer, It must be the formula 1/2 * ab sin c , can someone tell me what should I change to make it work.

#include <stdio.h>
#include <math.h>
float main ()
  {
float a,b,c,pi ;
printf("Enter a : ");
scanf("%f",&a);
printf("Enter b : ");
scanf("%f",&b); 
printf("Enter c :");
scanf("%f",&c);
printf("%f\n",(a*(1/2)*b*(c*pi)/180));
  
return 0;
}

Answer 1

The sub-expression (1/2) is always equal to 0 due to the integer arithmetic. You need to write for example (1.0f/2).

Apart from this the variable pi is not initialized

float a,b,c,pi ;

Also according to the C Standard the function main without parameters shall be declared like

int  main( void )