C语言程序从键盘输入一个三角形的三个边长a,b,c.计算面积

main()
{ float a,b,c,area,s;
scanf("%f,%f,%f",&a,&b,&c);
s=0.5*(a+b+c);
area=sqrt(s*(s-a)*(s-b)*(s-c));
printf("%f",area);

}

#include<stdio.h>
#include<math.h>
#define f(x,y,z) (x+y+z)/2
#define g(x,y,z) sqrt(f(x,y,z)*(f(x,y,z)-x)*(f(x,y,z)-y)*(f(x,y,z)-z))
void main()
{
float a,b,c,area;
scanf("%f %f %f",&a,&b,&c);
printf("\n");
while(a+b<=c||a+c<=b||b+c<=a)
{
printf("It isn't a triangle\n");
scanf("%f %f %f",&a,&b,&c);
printf("\n");
}
f(a,b,c);
area=g(a,b,c);
printf("The triangle's area is %15.10f\n",area);
}