Prove that : `cosx+cosy+cosz+cos(x+y+z)=4cos((x+y)/(2))cos((y+z)/(2))cos((z+x)/(2))`

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

Prove that : (cos x + cos y)^2 + (sin x - sin y)^2 = 4 cos^2\ (x+y)/2

Prove that : (cos x - cos y)^(2) + (sin x - sin y)^(2) = 4 sin^(2) ((x - y)/(2))

Given that cos(x-y) +cos (y-z) +cos (z-x)=-3/5 find cos x+ cos y + cos z

If x+y+z= pi/2 , prove that : cos(x-y-z) + cos(y-z-x) + cos (z-x-y)-4cosx cosy cosz=0

Find the value of the determinant |"cos"(x-y)"cos"(y-z)"cos"(z-x)"cos"(x+y)"cos"(y+z)cos(z+x)"sin"(x+y)"sin"(y+z)s in(z+x)|

To prove (cos5x+cos4x)/(1-2cos3x) = -cos2x-cosx

lf cos x + cosy-cos z = 0 = sin x + sin y + sin z then cos((x-y)/2)=

If 2(cos(x-y)+cos(y-z)+cos(z-x))=-3 , then :

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