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Palindrome Numbers, Compatible Numbers Multiplication Introduction Length of a Chord, Perimeter of a Segment Polygon Shapes Absolute Value Function Graph Time, Addition Difference and Sum of Two Cubes, SquaresClassifying Angles

Before looking at different angle types and their angle names, it helps to get an understanding of
degree measure involving angles.

In more basic Math, degree measure is the most common method of measuring angles.

The symbol for degrees is a small circle above the right side of a number.

So **45** degrees looks like **45°**.

A full rotation all the way around a full circle is **360°**.

A quarter of the way around a circle is **90°**.

Half way is **180°**, and three quarters around a circle is **270°**.

The angles of **35** degrees and **120** degrees inside a circle look like:

As will be seen further in the page. Angles of certain sizes have different angle names to identify
them.

It’s also true that angles don’t just go up to **360°** in size.

You can keep going after one full rotation of a circle as far as you like.

Such as in the image below where an angle of size **390°** is shown.

What size is the red colored angle in each of the following cases.

Red angle:

Classifying Angles

Different angle types have different names to identify them.

Below is a list of some of the most common angle types that can be encountered.

A right angle is an angle that is exactly **90°** in size.

Commonly illustrated as a square.

An acute angle is an angle that is of a size less than **90°.**

An obtuse angle is an angle that is larger than **90°**, but smaller than **180°** in size.

A straight angle is an angle that is exactly **180°** in size.

The angle on a straight line.

A reflex angle is an angle that is larger than **180°**, but smaller than **360°** in size.

Adjacent angles are angles that share a common point/vertex, and a common side, while not overlapping each other.

Depending on how an angle is measured, the angle can be in a positive or negative direction.

Positive is anti-clockwise, and negative is clockwise.

Congruent angles are simply angles that are the same size. Though they can look different.

The two angles below are congruent, they are the same size, just presented differently.

Angle Names Summary