Review the following types of angles: acute, right, obtuse, and straight.  Identify and draw types of angles in some practice problems.  

Summary of angle sizes

Angle typeAngle size (in degrees)
AcuteBetween 0, degree and 90, degree
RightExactly 90, degree
ObtuseBetween 90, degree and 180, degree
StraightExactly 180, degree

Right angles

A right angle is a 90, degree angle. A right angle is in the shape of a perfect corner, like the corner of a rectangular sheet of paper. Below is an example of a right angle.

Straight angles

A straight angle is a 180, degree angle. A straight angle looks like a straight line. Below is an example of a straight angle.

Acute angles

An acute angle is an angle whose degree measure is less than 90, degree. Below is an example of an acute angle.
When we compare an acute angle to a start color blueD, r, i, g, h, t, space, a, n, g, l, e, end color blueD, we can see that an acute angle is less than 90, degree.

Obtuse angles

An obtuse angle is an angle whose degree measure is greater than 90, degree but less than 180, degree. Below is an example of an obtuse angle.
When we compare an obtuse angle to a start color blueD, r, i, g, h, t, space, a, n, g, l, e, end color blueD, we can see that an obtuse angle is greater than 90, degree.
When we compare an obtuse angle to a start color greenD, s, t, r, a, i, g, h, t, space, a, n, g, l, e, end color greenD, we can see that an obtuse angle is less than 180, degree.
Want to learn more about angle types? Check out this video.

Practice set 1: Identify angles

Problem 1A
Is the following angle acute, right, obtuse, or straight?
Please choose from one of the following options.

Want to try more problems like this? Check out this exercise.

Practice set 2: Angles in diagrams and images

Problem 2A
What type of angle is the angle highlighted in green below?
Please choose from one of the following options.

Want to try more problems like this? Check out this exercise.

Practice set 3: Drawing angle types

Problem 3A
Drag the vertex of the angle to place the vertex at point A.
Drag another point on the angle to make one of the rays go through point B.
Make the other ray go through one of the unlabeled black points to create a straight angle.
The arc symbol near the vertex indicates the angle being measured.

Want to try more problems like this? Check out this exercise.