第四周项目1.3使用有默认参数的构造函数

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#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 showMassage();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::showMassage(){    cout<<"三角形的三边长分别是："<<a<<b<<c<<endl;    cout<<"三角形的周长是："<<perimeter()<<", 面积是："<<area()<<endl;}int main(){    Triangle Tri1;    Tri1.showMassage();    Triangle Tri2(1.5);    Tri2.showMassage();    Triangle Tri3(1.5,1.5);    Tri3.showMassage();    Triangle Tri4(7,8,9);    Tri4.showMassage();    return 0;}

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