求三角形面积

#include<stdio.h>
#include<math.h>
main()
{
double arc,a,b,c,s;
a=3.67;
b=5.43;
c=6.21;
s=(a+b+c)/2;
arc=sqrt(s*(s-a)*(s-b)*(s-c));
printf("a=%f\nb=%f\nc=%f\ns=%f\narc=%f\n",a,b,c,s,arc);	
return 0;
}