# Acute Angles

🏆Practice types of angles (right, acute, obtuse, flat)

## Definition of an acute angle

An acute angle is an angle that measures less than $90°$.

Acute angles can appear in triangles, parallelograms, and other geometric shapes where there is an angle less than $90°$ degrees.

### Acute angle

Which of the 4 angles presented in the figure corresponds to the description of the acute angle?

The correct answer is B) 40°

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

$$∢\text{ABC}$$ equal to 90°.

What angle is it?

If you are interested in learning more about other topics related to angles, you can check out one of the following articles:

• Angle Notation
• Sides, Vertices, and Angles
• Bisector
• Right Angle
• Obtuse Angle
• Straight Angle
• Vertically Opposite Angles
• Alternate Angles
• Corresponding Angles
• Sum of the Angles of a Triangle
• Sum of the Angles of a Polygon
• Sum and Difference of Angles

On the Tutorela website, you will find a wide variety of articles about mathematics

## Examples and exercises with solutions of acute angles

### Exercise #1

True or false?

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

### 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.

False

### Exercise #2

True or false?

The sum of two acute angles can be greater than 180 degrees?

False.

### Exercise #3

Does the drawing show an adjacent angle?

Not true

### Exercise #4

Does the drawing show an adjacent angle?

Not true

### Exercise #5

Choose the appropriate triangle according to the following:

Angle B equals 90 degrees.

## Review Questions

What is an angle?

An angle is the opening that occurs between two lines that join from a vertex. Angles can be measured in degrees or radians.

What is the classification of angles according to their measure?

Angles are classified into 6 types according to their measure:

• Acute angle
• Right angle
• Obtuse angle
• Straight angle
• Reflex angle
• Perigon angle or also called complete angle

What is an acute angle?

The acute angle is the narrowest angle of all according to its measure. In this case, an acute angle is one that measures less than $90^o$

Which of the following angles has a measure less than $90^o$ degrees?

A) Angle of $200^o$

B) Angle of $160^o$

C) Angle of $30^o$

Answer: In this case, option C is the angle that corresponds to an angle less than $90^o$, that is, it is an acute angle.

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