Definition Of Obtuse Angle

Any angle greater than 90° and smaller than 180° is called an Obtuse Angle.

More About Obtuse Angle

An angle of 90° is called a right angle.
An angle of 180° is called a straight angle.

Example of Obtuse Angle

The angle shown in the figure is greater than 90° but smaller than 180°, so it is an obtuse angle.

Video Examples: Acute and Obtuse Angles in Geometry

Solved Example on Obtuse Angle

Ques: Identify the obtuse angle in the given triangle.

Choices:

A. ∠ACB
B. ∠ABC
C. ∠BAC
D. ∠CAB
Correct Answer: B

Solution:

Step 1:An angle greater than a right angle and less than a straight angle (> 90° and < 180°)="" is="" called="" an="" obtuse="">
Step 2: In the given figure, ∠A and ∠C are acute angles and ∠B is an obtuse angle.
Step 3: So, ∠ABC is an obtuse angle.

Related Worksheet

• Classifying-Angles-Gr-4