# Complementary Angles

When the sum of the measures of two angles is 90°, such angles are called complementary angles and each angle is called a complement of the other.

The vertices of two angles may be same or different. In the given figure ∠AOB and ∠BOC are complementary as ∠AOB + ∠BOC = 30° + 60° = 90°.

Again, ∠PQR and ∠QRP are complementary as ∠PQR + ∠QRP = 40° + 50° = 90°.

Angles of measure 25° and 65° are complementary angles. The angle of 25° is the complement of the angle of 65° and the angle of 65° is the complement of the angle of 25°.

The complement of an angle of measure 32° is the angle of 58°. And, the complement of the angle of measure 58° is the angle of 32°.

Observations:

(i) If two are complement of each other, then each is an acute angle. But any two acute angles need not be complementary.

For example, angles of measure 30° and 50° are not complement of each other.

(ii) Two obtuse angles cannot be complement of each other.

(iii) Two right angles cannot be complement of each other.

Worked-out Problems on Complementary Angles:

1. Find the complement of:

(a) 68°

Solution:

90° - 68°

= 22°

Therefore, the complement of 68° is 22°

(b) 27°20'

Solution:

90° - 27°20'

= 89°60' - 27°20'

= 62°40'

Therefore, the complement of 27°20' is 62°40'

(c) x + 52°

Solution:

90° - (x + 52°)

= 90° - x + 52°

= 38° - x

Therefore, the complement of x + 52° is 38° - x

2. Find the complement of the angle (10 + y)°.

Solution:

Complement of the angle (10 + y)° = 90° - (10 + y)°

= 90° - 10° - y°

= (80 - y)°

3. Find the measure of an angle which is 46° less than its complement.

Solution:

Let the unknown angle be x, then measure of its complement = 90 - x

According to the question,

(90 - x) - x = 46°

90 - x - x = 46°

90 - 2x = 46°

90 - 90 - 2x = 46° - 90

-2x = 46° - 90

-2x = 46° - 90

-2x = -44°

2x = 44°

x = 44/2

x = 22°

Therefore, 90 - x (Put the value of x = 22°)

= 90 - 22°

= 68°

Therefore, the pair of complementary angles are 68° and 22°

Lines and Angles

Fundamental Geometrical Concepts

Angles

Classification of Angles

Related Angles

Some Geometric Terms and Results

Complementary Angles

Supplementary Angles

Complementary and Supplementary Angles

Adjacent Angles

Linear Pair of Angles

Vertically Opposite Angles

Parallel Lines

Transversal Line

Parallel and Transversal Lines

Didn't find what you were looking for? Or want to know more information about Math Only Math. Use this Google Search to find what you need.

### New! Comments

Have your say about what you just read! Leave me a comment in the box below. Ask a Question or Answer a Question.

Share this page: What’s this?

## Recent Articles

1. ### Comparison of Three-digit Numbers | Arrange 3-digit Numbers |Questions

Sep 13, 24 02:48 AM

What are the rules for the comparison of three-digit numbers? (i) The numbers having less than three digits are always smaller than the numbers having three digits as:

Read More

2. ### Worksheet on Three-digit Numbers | Write the Missing Numbers | Pattern

Sep 13, 24 02:23 AM

Practice the questions given in worksheet on three-digit numbers. The questions are based on writing the missing number in the correct order, patterns, 3-digit number in words, number names in figures…

Read More

3. ### 2nd Grade Place Value | Definition | Explanation | Examples |Worksheet

Sep 13, 24 01:20 AM

The value of a digit in a given number depends on its place or position in the number. This value is called its place value.

Read More

4. ### Comparison of Two-digit Numbers | Arrange 2-digit Numbers | Examples

Sep 12, 24 03:07 PM

What are the rules for the comparison of two-digit numbers? We know that a two-digit number is always greater than a single digit number. But, when both the numbers are two-digit numbers

Read More

5. ### Worksheet on Two Digit Numbers | Numbers in Words | Two-Digit Numbers

Sep 12, 24 02:09 AM

In worksheet on 2-digit numbers we will write the number which come before, after and in between, write the numerals, write the number names, place value and face value of 2-digit numbers, numbers in…

Read More