要求：分别用成员函数和友元函数来求圆的面积和周长。

Requirements: member function respectively, and a friend function to find area and circumference of a circle.

youdao

要求：分别用成员函数和友元函数来求圆的面积和周长。

Requirements: member function respectively, and a friend function to find area and circumference of a circle.

youdao