22:14:22 class Circle( float radius public: void Set- Radius(float r) radius=r float Get-Radiuso return radius float Girtho return 2*pi*radius float Areao return pisradius*radius; y 实际的程序中,类必须在使用之前定义22:14:22 class Circle{ float radius; public: void Set_Radius(float r){radius=r;} float Get_Radius(){return radius;} float Girth(){return 2*pi*radius;} float Area(){return pi*radius*radius;} }; 实际的程序中,类必须在使用之前定义