Theorem 1: For any real numbers x and y, sin x = sin y implies x = nπ +(– 1) n y, where n ∈ Z
Theorem 2: For any real numbers x and y, cos x = cos y, implies x = 2nπ ± y, where n ∈ Z
Theorem 3: If x and y are not odd mulitple of π / 2, then tan x = tan y implies x = nπ + y, where n ∈ Z
Numerical: Find the principal & general solutions of the equation sin x = ½