[" (viji) "cos4x-cos4y=8(cos x-cos y)(cos x+cos y)],[quad (cos x-sin y)(cos x+sin y)]

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

Prove that, cos 4 x - cos4 y = 8(cos x - cos y)(cos x + cos y)(cos x - sin x)(cos x + sin y)

(dy) / (dx) = (sin x-sin y) (cos x) / (cos y)

Solve y^'+y cos x=e^(sin x) cos x

cos y (dy) / (dx) + sin y cos x = sin x cos x

What ( sin x cos y + cos x sin y) (sin x cos y - cos x sin y) equal to ?

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

Prove that : (sin (x+y))/(sin (x-y) )= (sin x. cos y + cos x . Sin y)/(sin x. cos y-cos x. sin y)

Prove that : (sin (x+y))/(sin (x-y) )= (sin x. cos y + cos x . Sin y)/(sin x. cos y-cos x. sin y)