飛飛（二十一）求三角形的面积！

#include <iostream>
#include"cmath"

using namespace std;
class Triangle
{
public:
      void setABC(double x,double y,double z)
      {
            a=x;
            b=y;
            c=z;
      }
      double perimeter();
      double area();
      private:
      double a,b,c;
};
int main()
{
      Triangle tril;
      tril.setABC(4,5,6);
      cout <<"三角形的周长为： "<<tril.perimeter()<<"面积为： "<<tril.area()<<endl;
      return 0;
}
double Triangle::perimeter()
{
      return (a+b+c);
}
double Triangle:: area()
{
      return sqrt(((a+b+c)/2)*((a+b+c)/2-a)*((a+b+c)/2-b)*((a+b+c)/2-c));
}

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