I'm not sure what you don't understand, but what you posted is good.
Let's consider only the part within the square root.
I am fallowing the solution for a verify identity problem in my textbook, it looks like they multiply through with sin then cos in order to create tan functions under the radical. is this normal method to use? if they are using another method or identity can you explain.
this is exactly how it is in the book 4 I dont get or step 2.
I was not sure if multiplying through with sin or cos in order to advance to the next step was 'legal'. I was looking for a formula or a rule that would introduce sin or cos. but I guess you can just multiply through with trig functions as a general rule, correct?