`(sinx-siny)/(cosx+cosy)=tan(x-y)/(2)`

(cosx+cosy)^(2)|(sinx-siny)^(2)=4cos^(2)(x+y)/(2)

Prove that (cosx+cosy)^(2)+(sinx-siny)^(2)=4cos^(2)((x+y)/(2))

Prove that : (cosx+cosy)^(2)+(sinx-siny)^(2)=4cos^(2)""(x+y)/(2)

Prove that : (cosx-cosy)^(2)+(sinx-siny)^(2)=4sin^(2)""(x-y)/(2)

If (sinx)/(siny)=(1)/(2),(cosx)/(cosy)=(3)/(2) , where x,y in (0,(pi)/(2)) , then the value of tan (x+y) is equal to

Prove that (cosx + cosy)/(sinx - siny) = cot ((x-y)/2)

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

Prove that: (cosx-cosy)^2 +(sinx-siny)^2=4 sin^2frac (x-y)(2)

Prove the following: (cosx+cosy)^2+(sinx-siny)^2=4cos^2(frac(x+y)(2))