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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
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.
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.