#include <stdio.h>
int main()
  int math()                                                                    {
   float a,b,c,s,area;                                                               a=17.8  ;                                                                b=19.5 ;                                                                 c=25.7;                                                               s=(a+b+c)/2;                                                            area=sqrt s*(s-a)*(s-b)*(s-c);                                           printf("三角形面积为:%f\n",area);
    return 0;
        }