Obtuse Triangle

Lesson Objective

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

Study Tips

Tip #1

When one of the internal angle of a triangle is greater than 90°, this triangle can be called an obtuse triangle. See some examples below:

The math video below will explain more...

Math Video

Lesson Video

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Math Video Transcript

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In this lesson, we will learn about obt. triangles (OT).

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A triangle is an OT, when it has an internal angle that is greater than 90 degrees.

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Now, to demonstrate this, let's move vertex 'A' to the left

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Notice that, when the angle at vertex 'B' is greater than 90 degrees, this triangle becomes an OT.

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

00:00:40.100
Here, we get another OT, when the angle at vertex 'C', is greater than 90 degrees.

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Let's move vertex 'A'…and vertex 'C'.

00:00:55.220
Again, we get another OT, when the angle at vertex 'A' is greater than 90 degrees.

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Let's see some examples.

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Is this an OT? 

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Notice that, this angle is greater than 90 degrees.

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Therefore, this is an OT.

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Next example, how about this triangle?

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In this triangle, there are no angles that are greater than 90 degrees.

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Hence, this is not an OT.

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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 obtuse triangles or pick your choice of question below.

Question 1

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