# Types of Angles: Right, Straight, Acute & Obtuse

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• 0:00 What Is an Angle?
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Instructor: David Wood

David has taught Honors Physics, AP Physics, IB Physics and general science courses. He has a Masters in Education, and a Bachelors in Physics.

Angles are everywhere. Learn about the different types of angles we use in mathematics, including right angles, acute angles, obtuse angles, and straight angles. See if you can tell the difference with a quiz.

## What Is an angle?

An angle is a place where two lines intersect. Those lines could be on a piece of paper in a math class or they could be a real life lines, like the angle the side of a cup makes with the table it's sat upon. You can also measure angles between things that don't have actual physical lines. For example, you could measure the angle that a star is positioned above you.

Humans love to categorize things, even angles. There are four main types of angles that we name in mathematics. Those angle types are acute, obtuse, straight, and right.

## Types of Angles

A right angle is like a corner of a wall. The human world that is constructed with homes, offices, and meeting spaces is full of right angles. That's because right angles make things straight, and everyone likes it when things are straight. A right angle measures 90°, or quarter of a circle. The corners of most rooms are right angles. The corners of a square or rectangle are right angles. A right angle is probably the most common angle you see in human life.

An acute angle is an angle that is less than 90°. It is smaller than a right angle, and it doesn't matter whether this is 1° or 89°, it is still an acute angle.

But angles can of course be bigger than 90°. An angle that is larger than 90°, but smaller than 180° is called an obtuse angle. Again this can be 90.5° or 179.5°, it is still an obtuse angle.

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