Radian
A unit for angles: the length of arc the angle sweeps on a circle of radius 1. A full turn is 2π radians, about 6.28, and Python's math functions expect radians.
A full turn is 360 degrees, a number chosen long ago because it divides evenly in many ways. Mathematics and code usually use radians instead: the angle measured by the length of arc it sweeps out on a circle of radius 1. A full circle's edge is 2π long, so a full turn is 2π radians, about 6.283, and a half turn is π, about 3.142.
Try it now
As the angle goes round, cosine traces how far across you are and sine how far up. The curve drawn is the sine wave.
Learn it properly
Angles and waves · Radians, sine and cosine on the unit circle, the angle between embeddings, cycles and positions as waves. About 25 minutes.
Other terms from the same lesson
- sine wave: The smooth repeating curve traced by the height of a point going round the unit circle. Its amplitude is how far it swings; its period is how long one cycle takes.
- unit circle: The circle of radius 1 around the origin. Turning by an angle θ from (1, 0) lands on the point (cos θ, sin θ).
Never trained an AI?
Teach a small one to write, right in your browser. It takes about 20 seconds and needs no account.