Ratio of Sides

• cos θ = adj / hyp = b/c

• sin θ = opp / hyp = a/c

• tan θ = opp / adj = a/b

• Acronym to remember formulas: sohcahtoa

(sin opposite hypotenuse cos adjacent hypotenuse tan opposite adjacent)

• These properties are ratios, so the same equation can have multiple values (sin θ = 2/3 = 4/6 = 6/9)

Cosecant (CSC), Secant (SEC), Cotangent (COT)

• csc θ = 1 / sin θ

• sec θ = 1 / cos θ

• cot θ = 1 / tan θ

Know the following values to help solve problems

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

• cos 0° = 1 cos 30° = √ 3 / 2 cos 45° = √ 2 / 2 cos 60° = ½ cos 90° = 0

• tan 0° = 0 tan 30° = √ 3 / 3 tan 45° = 1 tan 60° = √ 3 tan 90° = undefined