Labeling the Sides

Hypotenuse (Longest, opposite 90°), Opposite (Across from the angle θ), Adjacent (Next to the angle θ).

SOH CAH TOA

Sin θ = Opp/Hyp, Cos θ = Adj/Hyp, Tan θ = Opp/Adj.

Finding a Side

Rearrange the formula and multiply or divide.

Example: Opp = Hyp × Sin θ

Finding an Angle

Use the inverse functions (sin⁻¹, cos⁻¹, tan⁻¹) on your calculator.

The Sine Rule

Formula: a/Sin A = b/Sin B = c/Sin C

The Cosine Rule (Side)

Formula: a² = b² + c² − 2bc Cos A

The Cosine Rule (Angle)

Formula: Cos A = (b² + c² − a²) / 2bc

Area of a Triangle

Formula: Area = ½ab Sin C

Exact Trig Values

Learn: Sin 30 = 0.5, Cos 60 = 0.5, Tan 45 = 1.