(KS2, Year 6)
The LessonComplementary 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 AnglesAngles of 30° and 60° are complementary angles.
30° + 60° = 90°
How to Find a Complementary Angle
QuestionWhat is the missing angle θ below?
The 53° angle and θ are complementary angles. They add up to 90°.
53° + θ = 90°
Subtract the 53° angle from 90°.
θ = 90° − 53° = 37°
Answer:The missing angle θ is 37°.
Lesson SlidesThe slider below shows another real example of complementary angles. Open the slider in a new tab
What Types of Angles Are Complementary?Complementary angles form a Corner.
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 AnglesBoth complementary angles are less than 90°, and so are acute angles.
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