Instructions on Compiling and Using Pi-Approx.c

To compile type 

gcc pi-approx.c -o pi-approx

This will create an executable file named pi-approx. Type

./pi-approx to run the program.

The program will prompt you to choose one of the four methods it uses
to approximate pi.

Method 1: The Gregory-Leibniz Series Approximation

	Once you've chosen the Gregory-Leibniz Series, the program will
	prompt you to choose the number of terms to go out in the series,
	as well as the number of digits to print out the result.

Method 2: The Gauss-Legendre Algorithm

        Once you've chosen the Gauss-Legendre Algorithm, the program will
        prompt you to choose the number of iterations to perform in the 
	algorithm, as well as the number of digits to print out the result.
	
Method 3: The Bailey-Borwein-Plouffe Formula

        Once you've chosen the Bailey-Borwein-Plouffe Formula, the program will
        prompt you to choose the number of terms to go out in the series,
        as well as the number of digits to print out the result.

Method 4: The Ramanujan Series Approximation

        Once you've chosen the Ramanujan Series, the program will
        prompt you to choose the number of terms to go out in the series,
        as well as the number of digits to print out the result.
 
The value of pi calculated will then be printed out to the requested accuracy.

The program will then prompt you to either approximate pi again, or close.

Each of the approximations is implemented in the program as a function.
They use scanf to read the number of terms/iterations and then calculate the 
value of pi, using their respective formulas. The Ramanujan series uses factorials,
which are implemented using a recursive function in the program.