` cos x = (cos y + cos z)/(1+cos y cos z)` Prove that `tan (x/2)= +- tan (y/2) tan (z/2)`

cos ^(-1) ""((cos x + cos y)/(1+cos x cos y))= 2 tan ^(-1) (tan ""(x)/(2) tan ""(y)/(2))

Prove that cos ^ (- 1) ((cos x + cos y) / (1 + cos x cos y)) = 2tan ^ (- 1) (tan ((x) / (2)) tan ((y) / (2)))

prove that tan ((pi) / (4) + (1) / (2) cos ^ (- 1) ((a) / (b))) + tan ((pi) / (4) - (1) / (2) cos ^ (- 1) ((a) / (b))) = (b) / (a) cos ^ (- 1) ((cos x + cos y) / (1 + cos x cos y) ) = 2tan ^ (- 1) ((tan x) / (2) (tan y) / (2))

If cos x + cos y + cos z =0 = sin + sin y +sin z then tan (x-y) =

If sin x + sin y + sin z = 0 and cos x + cos y + cos z = 0 then prove that cot (x+y)/2 = cot z and cos (x-y)/2 = pm 1/2

If cos x + cos y + cos z = 0 = sin x + sin y + sin then tan (xy) =

Show that cos^(-1) ((cosx+cos y)/(1+cos x.cosy))= 2tan^(-1)(tan(x/2).tan(y/2)) .

If cos x = k cos (x - 2y), then the value of tan (x -y).tan y is

If cos x = tan y, cos y = tan z and cos z = tan x, prove that sin x = sin y = sin z = sin18 ^ (@)