三角形类 （不给定实参）

#include <iostream>#include<Cmath>using namespace std;class Triangle{public :   Triangle(double x=1,double y=1,double z=1);   double perimeter();    double area();    void showMessage();private:    double a,b,c;};Triangle::Triangle(double x, double y, double z){    a=x;    b=y;    c=z;}double Triangle::perimeter(){    return (a+b+c);}double  Triangle::area(){    double s = (a + b + c) / 2;   return sqrt(s * (s - a) * (s - b) * (s - c));}void Triangle::showMessage(){    cout<<"三角形的三边长分别为："<<a<<' '<<b<<' '<<c<<endl;   cout<<"该三角形的周长为"<<perimeter()<<"，面积为"<<area()<<endl<<endl;}int main(){    Triangle Tri1;   Tri1.showMessage();    Triangle Tri2(1.5);    Tri2.showMessage();    Triangle Tri3(1.5,1.5);   Tri3.showMessage();   Triangle Tri4(7,8,9);    Tri4.showMessage();    return 0;}