To Prove:

Formula Used:

Proof:

LHS … (1)

Let x = tan A … (2)

Substituting (2) in (1),

LHS

= tan^-1 (tan 3A)

= 3A

From (2), A = tan^-1 x,

3A = 3 tan^-1 x

= RHS

Therefore, LHS = RHS

Hence proved.