Write a C++ program that calculates the Perimeter of a circle. The main function asks the user to input the diameter (i.e., d) of the circle. Then the main function calls another function to calculate...

Write a C++ program that calculates the Perimeter of a circle. The main function asks the user to input the diameter (i.e., d) of the circle. Then the main function calls another function to calculate the Perimeter of that circle. Finally, the main function displays the Perimeter of the circle. Recall that P e r i m e t e r space equals space 1 half pi space cross times space d space plus space