If sinx+siny = a, cosx+cosy = b, prove that sin(x+y) = `(2ab)/(a^(2)+b^(2))`

If sinx + siny =a and cos x +cos y =b , show that sin(x+y) = 2ab/(a^(2)+b^(2)) and tan (x-y)/2 = sqrt((4-a^(2) -b^(2))/(a^(2) +b^(2))

If sinx+siny=1/2 and cosx+cosy=1 , then tan(x+y)=

If sinx-siny=a and cosx+cosy=b,prove that tan((x+y)/2)=+-sqrt((4-a^2-b^2)/(a^2+b^2))

If sinx siny = 3 (cosy - cos x) then (sin3x)/(sin3y) =

If sinx + siny = 1/2 and cosx + cosy =1 , then tan(x + y)=.......

If sinx+siny=p,cosx+cosy=q then sec(x+y)=

If sinx/siny=1/2 and cosx/cosy=3/2 then sqrt(8+sec^2y)=