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

(cos x- cos y) ^(2) + (sin x - sin y) ^(2) =4 sin ^(2) "" ( x-y)/(2)

cos ^(2) 2x -cos ^(2) 6x = sin 4x sin 8x

(cos x + cos y ) ^(2) + (sin x - sin y ) ^(2) = 4 cos ^(2) ""(x + y )/( 2)

sin 2x + cos x =0

(sin x - sin y)/( cos x + cos y) = tan ""(x-y)/(2)

y = cos x + C : y' + sin x = 0

y - cos y = x : (y sin y + cos y + x)y' = y

(sin x + sin 3x )/( cos x + cos 3x )= tan 2x

alpha is a root of equation ( 2 sin x - cos x ) (1+ cos x)=sin^2 x , beta is a root of the equation 3 cos 2x - 10 cos x +3 =0 and gamma is a root of the equation 1-sin2 x = cos x- sin x : 0 le alpha , beta, gamma , le pi//2 cos alpha + cos beta + cos gamma can be equal to