### Isosceles Triangle

#### Lesson Objective

In this lesson, we will learn about Isosceles triangles...

#### About This Lesson

In this lesson, we will:

- learn what are isosceles triangles.
- 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.

### Study Tips

#### Tip #1

When a triangle has two sides (edges) of equal length, this triangle can be called an isosceles triangle. See some examples below:

#### Tip #2

Since this type of triangle has two sides of equal length, the base angles will definitely be the same. See some examples below:

The math video below will explain more...

### Math Video

#### Lesson Video

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#### Math Video Transcript

00:00:04.000

In this lesson, we will learn about isosceles triangle.

00:00:08.200

A triangle is an isos. triangle, when it has two sides of equal length.

00:00:15.040

Now, to demonstrate this, let's move vertex C to the right.

00:00:21.240

When these 2 sides have the same length, we get an isos. triangle.

00:00:28.140

Here, the side BC will be the base of this triangle.

00:00:34.060

Note that, since these 2 sides have the same length, these two base angles will also be the same.

00:00:43.120

Let's move vertex C and vertex B.

00:00:49.050

Notice that, we have another isos. triangle.

00:00:54.150

Now, there is a right angle. Therefore, this triangle can be called right isos. triangle.

00:01:04.120

Let's see some examples.

00:01:08.060

Is this an isos. triangle?

00:01:12.140

Since this triangle has 2 sides of equal length, this is an isos. triangle.

00:01:19.150

Next example, how about this triangle?

00:01:24.240

Notice that, these two angles are the same. Hence, these 2 sides must have the same length.

00:01:34.110

Hence, this is an isos. triangle.

00:01:39.000

Last example. Now, all the sides of this triangle do not have the same length.

00:01:47.130

Therefore, this is not an isos. triangle.

00:01:52.220

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 isosceles triangles or pick your choice of question below.

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