hello there iwas wandering if someone out there could help me.

i have been given a problem and i am really struggling to resolve a solution

if sin A + sin B = X

cos A + cos B = y

then prove sin (A+B)= (2xy)/(x^2+y^2)

if you can help thankyou

i have been trying to use the formula

a sin x+ b cos x = y =cos (x+z) to no avail haha