Obtuse Angle

Definition of Obtuse Angle

An obtuse angle is an angle that measures more than $90°$ degrees, but less than $180°$ degrees.

Acute angles can appear in triangles, parallelograms, and other geometric shapes.

Obtuse Angle

Detailed explanation

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Test yourself on types of aangles (right, acute, obtuse, flat)!

True or false?

One of the angles in a rectangle may be an acute angle.

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Examples and Exercises with Solutions for Obtuse Angles

Exercise #1

True or false?

One of the angles in a rectangle may be an acute angle.

Video Solution

Step-by-Step Solution

One of the properties of a rectangle is that all its angles are right angles.

Therefore, it is not possible for an angle to be acute, that is, less than 90 degrees.

Answer

False

Exercise #2

True or false?

An acute angle is smaller than a right angle.

Step-by-Step Solution

The definition of an acute angle is an angle that is smaller than 90 degrees.

Since an angle that equals 90 degrees is a right angle, the statement is true.

Answer

True

Exercise #3

Choose the appropriate triangle according to the following:

Angle B equals 90 degrees.

Video Solution

Step-by-Step Solution

Let's note in which of the triangles angle B forms a right angle, meaning an angle of 90 degrees.

In answers C+D, we can see that angle B is smaller than 90 degrees.

In answer A, it is equal to 90 degrees.

Answer

Exercise #4

Which figure depicts a right angle?

Video Solution

Step-by-Step Solution

A right angle is equal to 90 degrees.

In diagrams (a) and (c), we can observe that the angle symbol is a symbol representing an angle that equals 90 degrees.

Answer

Exercise #5

Which of the following angles are obtuse?

Video Solution

Step-by-Step Solution

By definition, an obtuse angle is an angle that is greater than 90 degrees. We can observe that in one drawing there is an angle of 90 degrees and therefore it is not an obtuse angle, the other two angles are less than 90 degrees meaning they are also not obtuse, they are acute angles.

Therefore, none of the answers is correct.