### Right Triangle

#### Lesson Objective

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

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.

### Study Tips

#### Tip #1

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

#### Tip #2

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

### Math Video

#### Lesson Video

Apple App Store (iOS) | Google Play (Android)

#### Math Video Transcript

00:00:03.190
In this lesson, we will learn about right-angled triangle (RT).

00:00:08.050
For a triangle, to be called a RT, one of its internal angles must be 90 degrees.

00:00:15.220
Now, let's move vertex 'A', and see what happens.

00:00:21.010
Notice that, when the angle at vertex 'B' becomes 90 degrees, this triangle becomes a RT.

00:00:29.210
Next, let's move this vertex, to the right.

00:00:34.140
Here, we get another RT, when the angle at vertex 'A' is 90 degrees. Let's continue.

00:00:45.240
Again, we get another RT, when the angle at vertex 'A' is 90 degrees.

00:00:54.000
As we move vertex 'A' further to the right, the angle at vertex 'C' becomes 90 degrees.

00:01:01.140
Therefore, we have another RT.

00:01:06.120
Now, observe the different sizes of a RT, when we move the vertex 'A' and 'C' together.

00:01:22.210
Let's see some examples.

00:01:26.080
Is this a RT?

00:01:29.150
Notice that, one of the internal angles is 90 degrees.

00:01:34.070
Therefore, this is a RT.

00:01:39.030

00:01:45.100
Now, none of these angles are 90 degrees.

00:01:49.200
Hence, this is not a RT.

00:01:54.130
That is all for this lesson.

### Practice Questions & More

#### 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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