Question

prove that sinx+siny/sinx-siny=tanx+y/2/tanx-y/2

Answer 1

notice that the answer(which we need to prove), contains tan of (x+y/2) divided by tan of (x-y/2), here the angles are (x+y/2) and (x-y/2) and now notice that the question has angles x and y that means you have to derive a relation between those two angles [(x+y/2),(x-y/2) and x,y] so i just searched the formula that satisfies the relation between those two angles as you can see on the image and figuring out which formula to use is rather easy it will hardly take a minute....