Trigonometric Identity Dependency 1 sin t sin t = csc1 t 1 sec t = cos t cos t = sec1 t 1 cot t = tan t 1 tan t = cot t csc t = tan t = cot t = sin2 θ + cos2 θ = 1 sin t cos t cos t sin t 1 + cot2 θ = csc2 θ tan2 θ + 1 = sec2 θ tan(−t) = − tan t sin(−t) = − sin t csc(−t) = − csc t cos(−t) = cos t sec(−t) = sec t cot(−t) = − cot t sin(u − v) = sin u cos v − cos u sin v sin(u + v) = sin u cos v + cos u sin v cos(u − v) = cos u cos v + sin u sin v cos(u + v) = cos u cos v − sin u sin v tan(u + v) = tan(u − v) = tan u+tan v 1−tan u tan v sin sec tan sin 2u = 2 sin u cos u cos 2u = cos2 u − sin2 u tan 2u = 2 tan u 1−tan2 u tan u−tan v 1+tan u tan v π 2 − θ = cos θ π 2 − θ = csc θ π 2 − θ = cot θ cos csc cot π 2 π 2 π 2 − θ = sin θ − θ = sec θ − θ = tan θ cos 2u = 1 − 2 sin2 u cos 2u = 2 cos2 u − 1 sin2 u = 1−cos 2u 2 2u cos2 u = 1+cos 2 2u tan2 u = 1−cos 1+cos 2u sin u cos v = 21 [sin(u + v) + sin(u − v)] cos u sin v = 12 [sin(u + v) − sin(u − v)] cos u cos v = 12 [cos(u + v) + cos(u − v)] sin u sin v = 12 [cos(u − v) − cos(u + v)] a+b a−b cos 2 2 a+b a−b sin a − sin b = 2 cos sin 2 2 a+b a−b cos a + cos b = 2 cos cos 2 2 a+b a−b cos a − cos b = −2 sin sin 2 2 sin a + sin b = 2 sin q v sin v2 = ± 1−cos q 2 v cos v2 = ± 1+cos q 2 v tan v2 = ± 1−cos 1+cos v