Trigonometry — Formula Sheet

sin θ = Opposite/Hypotenuse; cos θ = Adjacent/Hypotenuse; tan θ = Opposite/Adjacent

sin(90° - θ) = cos θ and cos(90° - θ) = sin θ

tan(90° - θ) = cot θ and cot(90° - θ) = tan θ

sin 0° = 0, sin 30° = 1/2, sin 45° = 1/√2, sin 60° = √3/2, sin 90° = 1

cos 0° = 1, cos 30° = √3/2, cos 45° = 1/√2, cos 60° = 1/2, cos 90° = 0

Three fundamental identities

sin²θ + cos²θ = 1, 1 + tan²θ = sec²θ, 1 + cot²θ = csc²θ