If `2cosx+2cos3x=cosy` and `2sinx+2sin3x=siny` then `cos2x=`

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

If cosx+cosy+cosalpha=0 and sinx + siny + sinalpha=0 , then cot((x+y)/2)=

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

(cosx-cosy)^(2)+(sinx-siny)^(2)=?

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

If sinx+siny+sinz=cosx+cosy+cosz=0, then (A) sin2x+sin2y+sin2z=0 (B) cos2x+cos2y+cos2z=0 (C) tanx+tany+tanz=0 (D) none of these