Types of Angles - Parts of an angle, Acute angle, Obtuse angle, Right angle, Straight angle, Reflex angle and Complete angle

Geometry is a branch in mathematics which deals with different angles, shapes, sizes and structures. The following are the most basic and common angles one should know. They are Acute angle, Right angle, Obtuse angle, Reflex angle, Straight angle, and complete angle. An angle is nothing but a geometrical figure that can simply be constructed by joining two rays at their endpoints. Angles are measured in degrees. They form one of the most important parts of geometry in maths. They are essential in the construction of complex geometrical shapes and figures.

Angles are formed when two rays of line inclined to each other combine with a common endpoint. Thus, an angle has two elements. They are the sides and the vertex. The side of an angle is categorized into the terminal sides and the initial sides (which can also be termed as the vertical sides).

Parts of an angle

• Vertex: This is the point (intersection point) where the rays meet.
• Arms: They are nothing but two straight lines from a vertex.
• Angle: When a ray of line is rotated at its endpoint, the inclination formed due to rotation between its initial position and final position is known as the value of an angle.

Angles are usually classified based on two main types. They are magnitude and direction. The following are the six varieties of angles based on their inclination. They are

• Acute angle
• Obtuse angle
• Right angle
• Straight angle (180°)
• Reflex angle
• Complete angle (360°)

Types of angles

• Acute angle: An acute angle is an angle that lies anywhere between 0 degrees and 90 degrees. In simple words, an acute angle is less than 90 degrees.

Obtuse angle: An obtuse angle can be considered opposite to an acute angle. This angle is capable of lying anywhere between 90 degrees and 180 degrees. In other words, an obtuse angle is larger than 90 degrees and lesser than 180 degrees.

• Right angle: The right angle is always equal to 90 degrees. So, any angle less than 90 degrees is an acute angle whereas, any angle greater than 90 degrees is an obtuse angle.
   

• Straight angle: A straight angle is obtained when a line makes 180 degrees while being measured. In simple words, a straight angle can be seen as a straight line because it makes 180 degrees between the arms.
   
• Reflex angle: The angle formed by measuring the outer angle of any acute, obtuse and right angle is known as a reflex angle. In other words, a reflex angle is nothing but any angle which measures more than 180 degrees but is less than 360 degrees.
   

• Complete Angle: A full rotation is nothing but an angle that is equal to 360 degrees. It can also be called a full angle. This angle is formed when one of the arms makes a complete rotation to form an angle.

There are two types of angles based on rotation. They are positive and negative angles. The pairs of angles are complementary angles, supplementary angles, adjacent angles, linear pairs and vertically opposite angles.