As, tan^–1(tan x) = x

Provided x ϵ

Here our x is 12 which does not belong to our range

We know tan(nπ –θ) = –tan(θ)

∴ tan(θ –2nπ ) = tan(θ)

Here n = 4

∴ tan(12–4π ) = tan(12)

Now 12–4π is in the given range

∴ tan^–1 (tan 12) = 12–4π.