Ideas required to solve the problem:

The general solution of any trigonometric equation is given as –

• sin x = sin y, implies x = nπ + (– 1)ⁿy, where n ∈ Z.

• cos x = cos y, implies x = 2nπ ± y, where n ∈ Z.

• tan x = tan y, implies x = nπ + y, where n ∈ Z.

Given,

⇒ {∵ sin θ = cos (π/2 – θ) }

If cos x = cos y then x = 2nπ ± y, where n ∈ Z

Clearly on comparing we have y = 3x

∴

, or

∴ or

Hence,

…ans