# Plane angle - Examples, Exercises and Solutions

## Definition of plane angle:

The plane angle is the one that measures $180°$.

### Plane angle

Which of the 4 angles shown in the figure corresponds to the description of the plane angle?

The correct answer is C) 180 °

## Examples with solutions for Plane angle

### Exercise #1

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 answer is correct.

True

### Exercise #2

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 #3

If the two adjacent angles are not equal to each other, then one of them is obtuse and the other acute.

### Step-by-Step Solution

The answer is correct because the sum of two acute angles will be less than 180 degrees and the sum of two obtuse angles will be greater than 180 degrees

True

### Exercise #4

Which figure depicts a right angle?

### Step-by-Step Solution

A right angle is equal to 90 degrees. In diagrams A+C, we see that the angle symbol is a symbol representing an angle that equals 90 degrees.

### Exercise #5

Choose the appropriate triangle according to the following:

Angle B equals 90 degrees.

### 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.

### Exercise #6

True or false?

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

False.

### Exercise #7

Does the drawing show an adjacent angle?

Not true

### Exercise #8

Does the drawing show an adjacent angle?

Not true

### Exercise #9

Does the drawing show an adjacent angle?

Not true

### Exercise #10

Does the drawing show an adjacent angle?

Not true

### Exercise #11

Does the drawing show an adjacent angle?

Not true

### Exercise #12

Does the drawing show an adjacent angle?

Not true

### Exercise #13

Does the drawing show an adjacent angle?

True

### Exercise #14

Which of the following angles is a plane angle?

### Exercise #15

Which figure shows a right angle?