Visual Reference
Key Diagrams
Unit Circle
Sine & Cosine Waves
SOH CAH TOA
Reference
Core Formulas
Pythagorean Identity
sin²θ + cos²θ = 1
The most fundamental trig identity — always true for any angle θ.
SOH CAH TOA
sin = opp/hyp · cos = adj/hyp
tan = opp/adj. Memorize this — it's the foundation of right triangle trig.
Law of Sines
a/sinA = b/sinB = c/sinC
Relates sides and opposite angles in any triangle.
Law of Cosines
c² = a² + b² − 2ab·cosC
Generalizes the Pythagorean theorem to any triangle.
Double Angle
sin2θ = 2sinθcosθ
cos2θ = cos²θ − sin²θ = 1 − 2sin²θ.
Reciprocal Identities
csc = 1/sin · sec = 1/cos
cot = 1/tan = cos/sin. These are the reciprocal trig functions.
Practice
Test Your Knowledge