设计一个三角形类（多文件）

#ifndef _TRIANGLE_
#define _TRIANGLE_
class Triangle {
private:
  double a, b, c;
public:
  Triangle();
  Triangle(double a, double b, double c);
  Triangle(Triangle &t);
  double getL();
  double getS();
  ~Triangle();
};
#endif

#include"Triangle.h"
#include<cmath>
Triangle::~Triangle(){}
Triangle::Triangle()
{
}
Triangle::Triangle(double a, double b, double c)
{
  this->a = a;
  this->b = b;
  this->c = c;
} 
Triangle::Triangle(Triangle &t)
{
  a = t.a;
  b = t.b;
  c = t.c;
}
double Triangle::getL()
{
  return a + b + c;
}
double Triangle::getS()
{
  double p = (a + b + c) / 2;
  return sqrt(p*(p - a)*(p - b)*(p - c));
}

#include"Triangle.h"
#include<iostream>
using namespace std;
int main()
{
  Triangle t1;
  Triangle t2(6,8,10);
  Triangle t3(t2);
  cout << t2.getL() << endl;
  cout << t3.getS ()<< endl;
  system("pause");
  return 0;
}