已知三角形的三边，求三角形的面积

小程序示例：

float area(float a, float b, float c){    float t, s;    t = (a + b + c) / 2;    s = (float)sqrt(t*(t - a)*(t - b)*(t - c));     //求得面积    return s;                                   //返回面积的值}int main(){    float s1, s2, s3,s4;    s1 = area(6.3, 4.0, 7.5);    s2 = area(7.5, 8.0, 3.7);    s3 = area(5.2, 8.0, 6.1);    s4 = s1 + s2 + s3;    printf("多边形面积为%.1f\n",s4);    system("pause");}

运行结果：

————————————————
2017.10.19
1：27