函数的声明与调用，函数的使用

编写一个函数，输入三角形的三条边长，求三角形的面积，输入输出功能在主函数实现，计算面积功能在子函数实现

作业还是要自己完成哦

#include<stdio.h>
#include<math.h>
double area(double x,double y,double z)
{
double p=x+y+z/2.0;
retunr sqrt((p*(p-x)*(p-y)*(p-z));
}
int main()
{
double a=1.0;
double b=1.0;
double c=1.0;
scanf("%lf %lf %lf",&a,&b,&c);
double ret = area(a,b,c);
printf("%lf",ret);
return 0;
}

#include <stdio.h>
#include <math.h>
double area(double a,double b,double c)
{
    double s = (a+b+c)/2;
    return sqrt(s*(s-a)*(s-b)*(s-c));
}
int main()
{
    double a,b,c;
    scanf("%lf%lf%lf",&a,&b,&c);
    if(a<=0 || b<=0 || c<=0 || a+b<c || a+c<b || b+c<a)
        printf("input error");
    else
       printf("area = %lf",area(a,b,c));
    return 0;
}

#include <stdio.h>
#include <math.h>
double func(double a, double b, double c)
{
    double s = 0;
    double result = 0;
    s = (a + b + c) / 2.0;
    result = sqrt(s * (s - a) * (s - b) * (s - c));
    return result;
}
int main()
{
    double a, b, c, s;
    scanf("%lf%lf%lf", &a, &b, &c);
    s = func(a, b, c);
    printf("%lf\n", s);
    return 0;
}