### Acute Triangle

#### Lesson Objective

In this lesson, we will learn about acute triangles.

#### About This Lesson

In this lesson, we will:

- Learn what are acute 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

All the internal angles of a triangle must be less than 90Â° for it to be an acute triangle. See the picture below:

#### Tip #2

Here are some examples of:

The math video below will explain more...

### Math Video

#### Lesson Video

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Acute Triangle from MathExpression.com on Vimeo.

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#### Math Video Transcript

00:00:03.230

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

00:00:08.200

For a triangle to be an acu. triangle, all the internal angles, must be less than 90 degrees.

00:00:17.120

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

00:00:23.210

Notice that, when this angle becomes 90 degrees, this triangle, is not an acu. triangle.

00:00:32.080

Next, as we continue to move this vertex, this angle is now greater than 90 degrees.

00:00:39.110

Hence, this triangle is not an acu. triangle.

00:00:45.160

Let's see some examples.

0:00:49.030

Is this an acu. triangle?

00:00:53.070

Since all the internal angles are less than 90 degrees, this is an acu. triangle.

00:01:00.080

How about this triangle?

00:01:04.020

Now, observe that, this angle is 90 degrees.

00:01:09.060

Since this angle is not less than 90 degrees, it is not an acu. triangle.

00:01:16.080

Last example, is this an acu. triangle?

00:01:22.120

Notice that, this angle is 110 degrees, which is greater than 90 degrees.

00:01:29.190

Therefore, this is not an acu. triangle.

00:01:34.120

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 acute triangles or pick your choice of question below.

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