An angle is a portion of the plane defined by two half-lines of the same origin. An angle is composed of a vertex and 2 lines. It's measured in degrees or radians (180° = n rad).

- A right angle is formed when the lines are perpendicular to each other.
- An obtuse angle is larger than a right angle.
- An acute angle is smaller than a right angle.
- When both lines overlap, the angle is null.
- When both lines are opposite, the angle is flat. The straight angle contains two right angles.

**Drag** the red points.

**Click** on the set square or the protractor to measure the angles.