It has been pointed out by Graham Rhodes that the value I gave in the radians example is not always valid from computer to computer. If you are planing on using this formula in code, you should consider initializing PI first: 
EXAMPLE:

C language:	PI=4.0*atan(1.0);
FORTRAN:	PI=4.0d0*datan(1.0)
Java:		PI=4.0*Math.atan(1.0);
This initialization is critical when you consider that not all processors can handle floating point precision the same. Hard coding PI to the value I gave you could be unpredicatably annoying.

So using JavaScript again it follows that if

PI=

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