An angle is formed when two rays share a common endpoint, called the vertex. Angles are measured in degrees (°) using a protractor.
Angles appear everywhere, from the hands of a clock to the folds of a hand fan as it opens. Even the corner of a sheet of paper forms an angle. They are classified based on their size and how open they are.
Types of Angles
Angles can be grouped into different types based on their measurements:
Acute Angles – Smaller than 90°
Right Angles – Exactly 90°
Obtuse Angles – Greater than 90° but less than 180°
Straight Angles – Exactly 180°, forming a straight line
Reflex Angles – Greater than 180° but less than 360°
Each type of angle has different properties and can be found in everyday objects.
Click on any angle type above to learn more!
Composite Angles and Angle Relationships
Sometimes, angles are formed by combining smaller angles. We can use angle relationships to describe how these smaller angles add up to form a larger angle.
For example:
- ∠YXV = 60°
- ∠VXW = 30°
Together, these two acute angles form ∠YXW, which is a right angle (90°):
Think of it as a part-part-whole relationship: the parts (60° and 30°) add up to the whole (90°).
Since ∠YXW is made up of two smaller angles, it is a composite angle: ∠YXW = ∠YXV + ∠VXW = 60° + 30° = 90°.
Practice Problems
Which of the following is an acute angle?
Which statement is true about an obtuse angle?
Fill in the blank.
A straight angle looks like:
An angle measuring 360° is a reflex angle.
