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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.

- Recognize geometric properties of an angle.
- Classify angles by name according to their measurements.
- Use the protractor and the set square to perform angle measurements.

An angle is measured with a **protractor** which represents a half circle divided into 180 sections. Each section measures 1°. It's the unit of measure for angles. To measure an angle, you…