• Author: Graham Mitchell
• Filename: AreaCalculator.java

### Area Calculator

Write a program to calculate the area of four different geometric shapes: triangles, squares, rectangles, and circles. You must use functions. Here are the functions you should create:

```public static double area_circle( int radius )              // returns the area of a circle
public static int area_rectangle( int length, int width )   // returns the area of a rectangle
public static int area_square( int side )                   // returns the area of a square
public static double area_triangle( int base, int height )  // returns the area of a triangle
```

Your program should present a menu for the human to choose which shape to calculate, then ask them for the appropriate values (length, width, radius, etc.). Then it should pass those values to the appropriate function and display the resulting area.

Notice that you must not input the values inside the functions, and you must not display the values inside the functions. All input and output must be in the `main()`, and values must be passed to the functions and returned from them.

shape formula
square A = s²
rectangleA = l × w
triangle A = ½bh
circle A = πr²

You'll need the value of π for `area_circle()`; feel free to use the built-in `double` variable called `Math.PI`.

The menu should keep looping until the human chooses to quit.

```Shape Area Calculator version 0.1 (c) 2005 Mitchell Sample Output, Inc.

-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

1) Triangle
2) Rectangle
3) Square
4) Circle
5) Quit
Which shape: 1

Base: 5
Height: 6

The area is 15.

-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

1) Triangle
2) Rectangle
3) Square
4) Circle
5) Quit
Which shape: 2

Length: 10
Width: 4

The area is 40.

-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

1) Triangle
2) Rectangle
3) Square
4) Circle
5) Quit
Which shape: 3

Side length: 9

The area is 81.

-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

1) Triangle
2) Rectangle
3) Square
4) Circle
5) Quit
Which shape: 4

The area is 50.2655.

-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

1) Triangle
2) Rectangle
3) Square
4) Circle
5) Quit
Which shape: 5

Goodbye.
```
```
```