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

If 2cosx+2cos3x=cosy and 2sinx+2sin3x=siny then cos 2x=

cosx - sin3x = cos2x

Let P(x)=sqrt(( cosx +cos2x+cos3x)^2+ (sin x + sin 2x+sin3x)^2) then P(x) is equal to

Let P(x)=sqrt(( cosx +cos2x+cos3x)^2+ (sin x + sin 2x+sin3x)^2) then P(x) is equal to

If cosx + cosy + cosz = 0 and sinx + siny + sinz =0 , then show that cos (x-y) + cos(y - z) + cos(z - x) = - 3/2.

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

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

If cosx + cosy + cosz = 0 "and" sinx + siny + sinz =0, "then show that" cos (x-y) + cos(y - z) + cos(z - x) = - 3/2.

If sinx+siny+sinz=3," then "cosx+cosy+cosz is equal to