What is tan inverse +cot inverse equal . Plz do tell the solution of proving

tan^-1x + cot^-1x = π/2, x ∈ R

Proof-

Let tan^-1 x = y

⇒ x = tan y

⇒ x = Cot (π/2 - y) ['.' tan θ = cot(π/2 - θ)]

⇒ cot^-1x = cot^-1[Cot (π/2 - y)]

⇒ cot^-1x = π/2 - y

⇒ cot^-1 x + y = π/2

⇒ cot^-1 x + tan^-1x = π/2