#include<stdio.h>
#include<math.h>
int main()
{
    double triangle_area(double a, double b, double c);
    double a, b, c,area=0;
    printf("请输入三角形的三条边：");
    scanf_s("%lf,%lf,%lf\n", &a, &b, &c);
    area = triangle_area(a, b, c);
    printf("三角形的面积为：%f", area);
    return 0;
}

double triangle_area(double a, double b, double c)
{
    double p, s;
    p = (a + b + c) / 2;
    s = sqrt(p * (p - a) * (p - b) * (p - c));
    if (a + b > c && b + c > a && a + c > b)
        return (s);
    else return (0.0);
}