Question

Proof:

Answer 1

:)

Answer 2

\[\tan 3a = \frac{ 3 \tan a - \tan³ a }{ 1 -3\tan² a }\]

Answer 3

I was thinking of starting with the LHS as tan (2a + a) but that runs into a dead end for me

Answer 4

No, focus on the more complicated side. :)

Answer 5

The RHS ressembles to this formula

\[\tan 2a = \frac{ 2\tan a}{ 1- \tan² a}\]

But as far as I know, if you multiply the a, you get tan x a, and not x tan a, so thats where i'm stuck

Answer 6

solving by converting tan in terms of sin and cos will be much easier