C语言高手，救教一道C语言编程问题，如能帮助，万分感谢

Question

已知：a=3.5,b=5.4,c=4.3,编程以求a,b,c为边长的三角形的面积Area=___
提示：Area=根号下s(s-a)(s-b)(s-c) 其中S=a+b+C/2

Answer 1

#include<stdio.h>
#include<math.h>
void main()
{
float a=3.5,b=5.4,c=4.5;
float s,area;

s=a+b+c/2;
area=sqrt(s*(s-a)*(s-b)*(s-c));
printf("area=%f",area);
}

Answer 2

//通过运行
#include<stdio.h>
#include<math.h>
main()
{
float a=3.5,b=5.4,c=4.3,area,s;
s = a+b+c/2;
area = sqrt(s*(s-a)*(s-b)*(s-c));
printf("%f\n",area);
getch();
}

Answer 3

#include <stdio.h>
#include <math.h>

int main()
{
double a=3.5;
double b=5.4;
double c=4.5;
double s;
double area;

s=(a+b+c)/2;
area=sqrt(s*(s-a)*(s-b)*(s-c));
printf("Area = %f \n",area);
return 0;
}

编译过了，应该么问题！