Write a geometry calculator in C$++.$ make the menu can be run until the user quits.

Add the following functions to display the menu, validate the user inputs and calculate the area of a circle, rectangle and triangle:

void showMenu$()$; $//$display the menu

void areaCircle$()$; $//$ ask for user input and validate the value of radius until it is $>=0$ then display the area

void areaRectangle$()$; $//$ ask for user input and validate the values of length and width until both are $>=0$ then display the area

void areaTriangle$()$; $//$ ask for user input and validate the values of base and height until both are $>=0$ then display the area