Right Triangle

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Lesson Objective

In this lesson, we will learn about right triangles (also called right-angled triangle)...

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About This Lesson

In this lesson, we will:

  • learn what are right triangles.
  • see some examples on identifying them.

The study tips and math video below will explain more.

right triangle example

Study Tips

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Tip #1

When one of the internal angle of a triangle is equals to 90°, this triangle can be called a right triangle. See the examples below:

examples of right triangles
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Tip #2

A right triangle can also be an isosceles triangle if the two sides that form the 90° angle are equal in length. See the picture below:

a right triangle can also be an isosceles triangle

Math Video

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Lesson Video

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Math Video Transcript

In this lesson, we will learn about right-angled triangle (RT).

For a triangle, to be called a RT, one of its internal angles must be 90 degrees.

Now, let's move vertex 'A', and see what happens.

Notice that, when the angle at vertex 'B' becomes 90 degrees, this triangle becomes a RT.

Next, let's move this vertex, to the right.

Here, we get another RT, when the angle at vertex 'A' is 90 degrees. Let's continue.

Again, we get another RT, when the angle at vertex 'A' is 90 degrees.

As we move vertex 'A' further to the right, the angle at vertex 'C' becomes 90 degrees.

Therefore, we have another RT.

Now, observe the different sizes of a RT, when we move the vertex 'A' and 'C' together.

Let's see some examples.

Is this a RT?

Notice that, one of the internal angles is 90 degrees.

Therefore, this is a RT.

Next example, how about this triangle?

Now, none of these angles are 90 degrees.

Hence, this is not a RT.

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 right triangle or pick your choice of question below.

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