Written by the Fiveable Content Team • Last updated September 2025
Verified for the 2026 exam
Verified for the 2026 exam•Written by the Fiveable Content Team • Last updated September 2025
Definition
The cosine function relates an angle (in radians) to its x-coordinate on the unit circle. It also oscillates between -1 and 1, but starts from 1 instead of 0 like sin(x).
Related terms
Unit circle: A circle with a radius of 1 unit, often used to define trigonometric functions.
Trigonometric identities: Equations that relate different trigonometric functions to each other.
Periodicity: The property of a function that repeats itself after a certain interval.