Geometry: Types of Angles
Identify and classify right angles, acute angles, and obtuse angles in shapes and real life.
What You Need to Know
Key Concept Diagram
An angle is the amount of turn between two lines that meet at a point called the vertex.
A right angle is exactly 90° and is shown with a small square.
An acute angle is less than 90°; an obtuse angle is greater than 90° but less than 180°.
Squares and rectangles have four right angles; triangles can have one right angle.
Key Vocabulary
angle
The space between two straight lines that meet at a point, measured in degrees.
right angle
An angle that measures exactly 90 degrees.
acute angle
An angle that measures less than 90 degrees.
obtuse angle
An angle that measures more than 90 degrees but less than 180 degrees.
Knowledge Check
Select the correct answer for each question. Click "Check Answer" to see if you are right.
Question 1
A corner of a square tile is what type of angle?
Question 2
An angle that is 55° is best described as:
Question 3
Which angle is greater than 90° but less than 180°?
Key Concepts Summary
- ●An angle is the amount of turn between two lines that meet at a point called the vertex.
- ●A right angle is exactly 90° and is shown with a small square.
- ●An acute angle is less than 90°; an obtuse angle is greater than 90° but less than 180°.
- ●Squares and rectangles have four right angles; triangles can have one right angle.