trignometric identities

Pythagorean Identities

sin² θ + cos² θ = 1

tan² θ + 1 = sec² θ

cot² θ + 1 = csc² θ

Ratio Identities

sin (–x) = –sin x

cos (–x) = cos x

tan (–x) = –tanx

csc (–x) = –csc x

sec (–x) = sec x

cot (–x) = –cot x

sin (90° – x) = cos x

tan (90° – x) =cotx

sec (90° – x) = csc x

cos (90° – x) = sin x

cot (90° – x) = tan x

csc (90° – x) = sec x

Double Angle Identities