Written by the Fiveable Content Team • Last updated August 2025
Verified for the 2027 exam
Verified for the 2027 exam•Written by the Fiveable Content Team • Last updated August 2025
Definition
The fundamental trigonometric identity sin² θ + cos² θ = 1, derived from the Pythagorean Theorem applied to a right triangle with a point on the unit circle at coordinates (cos θ, sin θ).
AP course connection
Topic 3.12: 3.12 Equivalent Representations of Trigonometric Functions