Angles
Two rays sharing an endpoint; measured in degrees.
Key idea
Two rays sharing an endpoint; measured in degrees.
In depth
An angle is the amount of turn between two rays that share a vertex. It is measured in degrees (a full turn is 360°) or radians. The size does not depend on how long the rays are drawn.
Worked example
A clock at 3:00 has hands at 90° to each other, since a quarter of 360° is 90°.
Real-world uses
- Setting the slope of a ramp
- The angle of a camera view or a steering turn
Common mistake
Judging an angle by how long its arms look. Only the opening matters.
How to learn this
- Read the key idea and say it in your own words.
- Work through the worked example, then try a similar problem.
- Use the interactive lesson’s visual and mini-quiz to check the pattern.
Frequently asked questions
What is Angles?
Two rays sharing an endpoint; measured in degrees. It is a topic at the beginner level in Geometry.
Where is Angles used in real life?
Real-world examples: Setting the slope of a ramp; The angle of a camera view or a steering turn.
What should I learn before Angles?
Make sure you are comfortable with Line Segments and Rays, the previous topic in Geometry.
What is a common mistake with Angles?
Judging an angle by how long its arms look. Only the opening matters.
How can I practise Angles?
Open the interactive lesson, play with the visual, then answer the three-question mini-quiz. Getting two right marks the topic complete.
What comes after Angles?
Move on to Types of Angles next.
Related beginner topics in Geometry
- Points, Lines and Planes – The undefined building blocks of geometry.
- Line Segments and Rays – A segment has two endpoints; a ray starts at a point and goes on forever.
- Types of Angles – Acute <90°, right 90°, obtuse between 90° and 180°, straight 180°.
- Measuring Angles with a Protractor – Align the baseline and read the scale.
- Complementary and Supplementary – Pairs summing to 90° or 180°.
- Triangles: Classification – By sides (equilateral, isosceles, scalene) and by angles.