Area of a Triangle in C

#include<stdio.h>
#include<conio.h>
main()
{
float s1,s2,s3,S,area;
float tri_area();
printf("Enter the three sides of a triangle\n");
scanf("%f%f%f",&s1,&s2,&s3);
area=tri_area(s1,s2,s3);
printf("The area of the triangle is = %f\n",area);
getch();
return 0;
}


float tri_area(a,b,c)
{ 
float S,area;
S=(a+b+c)/2;
area=sqrt(S*(S-a)*(S-b)*(S-c));
return(area);
}