Angles form the core of the geometry in mathematics. They are the fundamentals that eventually lead to the formation of the more complex geometrical figures and shapes. Lets us begin with the study of different types of angles to get a better understanding of the topic.
When two rays combine with a common end point and the angle is formed.
The two components of an angle are “sides” and “vertex”. The side can be categorized into terminal sides and initial sides (or vertical sides) as shown in the image below.
These two rays can combine in multiple fashions to form the different types of angles in mathematics.
Let us begin by studying these different types of angles in geometry.
Types of Angles
The images below illustrate certain types of angles.

Acute Angle
An acute angle lies between 0 degrees and 90 degrees or in other words, an acute angle is one that is less than 90 degrees. The figure below illustrates an acute angle.

Obtuse Angle
An obtuse angle is the opposite of an acute angle. It is the angle which lies between 90 degrees and 180 degrees or in other words, an obtuse angle is greater than 90 degrees and less than 180 degrees. The figure below illustrates an obtuse angle.

Right Angle
A right angle is always equal to 90 degrees. Any angle less than 90 degrees is an acute angle whereas any angle greater than 90 degrees is an obtuse angle. The figure below illustrates a right angle or a 90degree angle.

Straight Angle
A straight angle is 180 degrees when measured. The figure below illustrates a straight angle or a 180degree angle. You can see that it is just a straight line because the angle between its arms is 180 degrees.

Reflex Angle
Since this measurement is less than 90 degrees, the arms form an acute angle. But what about the angle on the other side? What is the larger angle that is complementary to the acute angle called?
It is called a reflex angle. The image below illustrates a reflex angle.
Any angle that has a measure which is greater than 180 degrees but less than 360 degrees (which coincides with 0 degrees), is a reflex angle.
About Angles
The following points can be kept in mind while dealing with angles.
 Positive angle – Angle measured counterclockwise from the base
 Negative Angle – Angle measured clockwise from the base
The parts of an angle are
 Vertex – Point where the arms meet
 Arms – Two straight line segments from a vertex
 Angle – If a ray is rotated about its endpoint, the measure of its rotation is called angle between its initial and final position
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