#include <iostream>
#include <iomanip>
#include <cmath>
using namespace std;

int main ()
{



	//Declaration of Variables.
	double circleArea, rectangleArea, triangleArea,
		length, width, height, base, radius;
	char choice;
	const double PI = 3.14159;


	//Display the menu.

	cout << "\tGeometry Calculator" << endl << endl;
	cout << setw(10) << "1. Calculate the Area of a Circle" << endl;
	cout << setw(10) << "2. Calculate the Area of a Rectangle" << endl;
	cout << setw(10) << "3. Calculate the Area of a Triangle" << endl;
	cout << setw(6) << "4. Quit" << endl;

	cout << endl;

	//Prompt User for choice.

	cout << "Enter your choice (1-4)" << endl;
	cin >> choice;
	cout << endl;


	//Calculate the area of a Circle.

	switch (choice)
	{

	case 'C':
	case 'c':
	case '1':

		cout << "Enter the radius of the circle: ";
	    cin >> radius;

		if (radius < 0)
		{
			cout << "Number must be greater than 0. Try again" << endl;
		}
		else
		{
			circleArea = PI * pow(radius, 2);
			cout << "The area of the circle is: " << circleArea;
		}

		cout << endl;

		break;


	//Calculate the area of a Rectangle.

	case 'R':
	case 'r':
	case '2':

		cout << "Enter the length and width of the rectangle: ";
		cin >> length >> width;

		if (length < 0 || width < 0)
		{
			cout << "Number must be greater than 0. Try again" << endl;
		}
		else
		{
			rectangleArea = length * width;
			cout << "The area of the rectangle is: " << rectangleArea;
		}

		cout << endl;

		break;


	//Calculate the area of a Triangle.

	case 'T':
	case 't':
	case '3':

		cout << "Enter the base and height of the triangle: ";
	    cin >> base >> height;

		if (base < 0 || height < 0)
		{
			cout << "Number must be greater than 0. Try again" << endl;
		}
		else
		{
			triangleArea = base * height * .5;
			cout << "The area of the triangle is: " << triangleArea;
		}

		cout << endl;

		break;


	//Quit the program.

	case 'Q':
	case 'q':
	case '4':

		cout << "End of Program" << endl;
		cout << endl;

		break;


	//Invalid number.

	default:

		cout << "That is an invalid choice." << endl;
		cout << "Please select choices 1-4." << endl;

		break;
	}

	return 0;
}