is(cos x+cos y)/(cos y-cos x)=cot((x+y)/(2))cot((x-y)/(2))

(cos x + cosy)/(cos y -cos x) = cot ((x+y)/(2)) cot ((x-y)/(2))

(sin 2x - sin 2y)/(cos 2y-cos 2x) = cot (x+y)

Show that (i) cos x+cos y=2 cos (x+y)/(2) cos (x-y)/(2) (ii) cos x-cos y=-2 sin (x+y)/(2) sin (x-y)/(2) (iii) sin x+sin y=2 sin (dot(x)+y)/(2) cos (x-y)/(2) (iv) sin x-sin y=2 cos (x+y)/(2) sin (x-y)/(2)

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

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

If cos x=3 cos y, then 2 tan ((y-x)/(2))= ............. A) cot ((y-x)/(2)) B) cot ((x+y)/(4)) C) cot ((y-x)/(4)) D) cot ((x+y)/(2))

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

If cos x + cos y - cos (x + y ) =3/2, the

cos4x-cos4y = 8 (cos x-cos y) (cos x + cos y) (cos x-sin y) (cos x + sin y)