1) sin(x+y)sin(x-y) = cos^2 y - cos^2 x

(sin x cos y + cos x sin y)(sin x cos y - cos x sin y) = cos^2 y - cos^2 x

From there I don't know where to go...

2) tan(pi/4 + x) + tan(pi/4 - x) = 2sec2x

For this one I don't even know where to start, I can't even find a formula that I could use for the LS.

All and any help is very much welcomed!

Thanks in advance:)