Complementary Angles

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Lesson Objective

In this lesson, we will learn about complementary angles.

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About This Lesson

In this lesson, we will learn:

  1. What are complementary angles
  2. See some examples on identifying them

The study tips below will give you a short summary on this.

The math video below will explain in depth about this. Furthermore, it will show some examples so that you can understand this lesson better.

complementary angles

Study Tips

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Tip #1

When we add two angles and get 90°, we can say that these angles are complementary angles. See an example below:

examples of complementary angles

The math video below will explain more on this.

Math Video

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Lesson Video

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Math Video Transcript

In this lesson, we will learn about comp. angles.

Let's take a look at these two angles.

Notice that, when we add these two angles, we get 90 degrees.

Seeing this, we can say that these two angles are comp. angles.

Now, when we rotate this arm, these two angles must add to 90 degrees, to remain as comp. angles.

Adding 15 degrees with 75 degrees, gives 90 degrees.

Adding 67 degrees with 23 degrees, gives 90 degrees.

Now, let's see some examples.

Are these comp. angles?

To find out, we just need to add 12 degrees with 78 degrees. This gives 90 degrees.

Hence, these are angles that are complementary.

Next example, these two angles are comp. angles. Find x.

We know that, when we add these 2 angles, we must get 90 degrees.

Hence, we can find 'x', by subtracting 90 degrees, with 73 degrees.

Therefore, ‘x’ will be equals to 17 degrees.

That is all for this lesson.

Practice Questions & More

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Multiple Choice Questions (MCQ)

Now, let's try some MCQ questions to understand this lesson better.

You can start by going through the series of questions on complementary angles or pick your choice of question below.

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