If `3cosx + 2cos3x=cosy`, `3sinx + 2sin3x =siny`, then `cos2x` equals

If 3cos x+2cos3x=cos y3sin x+2sin3x=sin y, then cos2x equals

If 3cos x+2cos3x=cos y3sin x+2sin3x=sin y, then the value of cos2x is

If cosx + cosy + cosz = 0 = sinx + siny + sinz ,then possible value of cos((x-y)/2) is (A) 4 3 1 2 (B) 4 3 2 1 (C) 3 4 2 1 (D) 3 4 1 2

If cosx+cosy+cosz=sinx+siny+sinz=0" then "cos(x-y)=

If cos x. cosy+sinx.siny=-1 then cosx+cosy is :

If 1 + cos x cos y + sin x sin y = 0 , then which of the following is / are true 1. cosx + cosy = 0 2. sinx + siny = 0 3. sinx + cosy = 0 chose the correct option from the code given below