`(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)

cos x + cos y = (4) / (5), cos x-cos y = (2) / (7) rArr14tan ((xy) / (2)) + cot ((x + y) / (2)) =

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 x + cos y = (4) / (5), cos x-cos y = (2) / (7) rArr14tan ((xy) / (2)) + 5cot ((x + y) / (2)) =

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)

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

If x= cot A + cos A and y= cot A - cos A, prove that ((x-y)/(x+y))^(2)+((x-y)/(2))^(2)=1.

dy/dx + y cot x = 2 cos x

If cos (x-y)=3 * cos (x+y) , " then " cot x* cot y=

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