第五周项目1.4

#include <iostream>#include<cmath>using namespace std;class Triangle{public:    Triangle(double x=1.0,double y=1.0,double z=1.0);//构造函数    double perimeter();//计算三角形的周长    double area();//计算并返回三角形的面积    void showMessage();private:    double a,b,c;//三边为私有成员数据};Triangle::Triangle(double x,double y,double z){    a=x;    b=y;    c=z;}void Triangle::showMessage(){    cout<<"三角形的周长为："<<perimeter()<<'\t'<<"面积为："<<area()<<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;}double Triangle::perimeter(){    return a+b+c;;}double Triangle::area(){    double x,y;    x=(a*a+b*b-c*c)/(2*a*b);    y=sqrt(1-x*x);    return 0.5*a*b*y;}