rationalizeI'm afraid I'm lost attempting to solve what is probably a really simple problem. The idea is to get an exact answer using the trigonometric difference identity for tangent.

which is the same as

\\edit:

the formula is

thus

ergo

\\edit

and this is where I'm stuck. The book has the answer as , so either I'm completely wrong, or I just don't know how to simplify properly. Any assistance would be greatly appreciated.

hint :