Find all solutions in the interval [0, 2π). cos x = sin x

Cos x = Sin x

Sin x = Cos x

Sin x / Cos x = Cos x / Cos x

Tan x = 1

tan (45) = 1

tan Θ = y/x;

x = π/4; 5π/4

Using the unit circle for cos x = sin x

sin Θ = y

cos Θ = x

x = y

⇒ π/4 or 45° ⇒ (√2/2, √2/2)

⇒ 5π/4 or 225° ⇒ (-√2/2, - √2/2)