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# Complementary Angles

(KS2, Year 6)

## The Lesson

Complementary angles are two angles which add up to a right angle (90°).Two angles that add to 90° are are said to complement each other.

## A Real Example of Complementary Angles

Angles of 30° and 60° are complementary angles.
30° + 60° = 90°

## How to Find a Complementary Angle

## Question

What is the missing angle θ below?## Step-by-Step:

# 1

The 53° angle and θ are complementary angles. They add up to 90°.

53° + θ = 90°

# 2

Subtract the 53° angle from 90°.

θ = 90° − 53° = 37°

## Answer:

The missing angle θ is 37°.## Top Tip

## What Types of Angles Are Complementary?

**C**omplementary angles form a

**C**orner.

## Note

## What's In an Name?

Complementary comes from the Latin word "complementum" meaning "fill up, complete, supply. This is because an acute angle is filled up to form a right angle. We get the word "complete" from the same root. Don't confuse a complementary angle with a complimentary angle; which would be a free angle or an angle giving praise.## Complementary Angles Are Acute Angles

Both complementary angles are less than 90°, and so are acute angles.**Help Us To Improve Mathematics Monster**

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