this post might be of some help, there are others. i'll try to look them up
http://www.mathhelpforum.com/math-he...equations.html
As promised:
http://www.mathhelpforum.com/math-he...er-radius.html
http://www.mathhelpforum.com/math-he...te-square.html
http://www.mathhelpforum.com/math-he...ative-qus.html
http://www.mathhelpforum.com/math-he...ng-sqaure.html
it's not much, but it should get you started