If k is an integer, sin(θ + 2kπ) = sin θ cos(θ + 2kπ) = cos θ tan(θ + πk) = tan θ cosec(θ + 2kπ) = cosec θ sec(θ + 2kπ) = sec θ cot(θ + πk) = cot θ

sin(π - θ) = sin θ

cos(π - θ) = -cos θ