Would anyone with more maths experience please show me step by step how to, or at least tell me how to.
NB: copying the above equations to http://www.wolframalpha.com/ will give a better visual representation of the problem.
Never mind, I solved it (okay well I had help). First you times out the fraction's square. Then you subtract the one. And realising that the final answer squared is now under the root, you have just proved what you set out to do.