triangle in c

#include<stdio.h>
#include<stdlib.h>
#include <math.h>
int calculate(double a,double b, double c, double* p, double* s){
    *p =  a+b+c;
    *s = sqrt(*p/2 *(*p/2 -a)*(*p/2 -b)*(*p/2 - c));
return 0;
}
int main(){
double a = 20;
double b = 10;
double c = 10;
double p = 0.0;
double s = 0.0;
calculate(a,b,c,&p,&s);
printf("%lf",p);
printf("%lf",s);

return 0;
}