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,

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

From above expression and on comparison with standard equation we have:

y = 2x

∴ 4

Hence,

or

∴ or

⇒ x = nπ or

∴ where m, n ϵ Z ..ans