Question

How do you verify `1 + tanxtan2x = sec2x`?

Answer 1

`(1 + sin x.sin 2x)/(cos x.cos 2x) =`

`= (cos x.cos 2x + sin x.sin 2x)/(cos x.cos 2x) =`

`= cos (2x - x)/(cos x.cos 2x) = 1/cos (2x)` = sec 2x