---
tag: 03YN70NK0Z
kind: concept
name: Oriented angle
aliases: [signed-angle, directed-angle]
msc: [51M05]
sources:
  - url: https://en.wikipedia.org/wiki/Angle
    locator: Signed angles
---

## Summary

An oriented angle in the plane measures the turn from one direction to another, with a sign. Anticlockwise turns are positive and clockwise turns are negative. It is defined modulo a full turn $2\pi$, and it changes sign when you swap the two directions.