Question

Question #edfc6

Answer 1

Prove trig identity

Explanation:

Apply the trig identity:
cos (x + y) = cos x.cos y - sin x.sin y
Left side:
`LS = 1 - (sin x/cos x)(sin y/cos y) = 1 - (sin x.sin y)/(cos x.cos y) =`
`(cos x.cos y - sin x.sin y)/(cos x.cos y) = (cos (x + y))/(cos x.cos y)`