c++应用编程200例part2：根据半径计算圆的周长和面积-c++ application programming 200 cases part2: calculated according to the radius of the area and circumference of a circle

c++应用编程200例part4：根据半径计算圆的周长和面积-c++ application programming 200 cases part4: calculated according to the radius of the area and circumference of a circle