[Maths Class Notes] on Reflex Angle Pdf for Exam

As per the Euclidean geometry, the formation of an angle takes place when two rays meet at a common point. These two rays are termed as sides, and the meeting point is called the vertex. Moreover, angles are also formed due to the intersection of two curves, two planes, etc. 

A figure showing parts of an angle

• Turn between the two straight lines is called the angle.

• Corner point is the vertex.

• The two straight lines are arms.

Besides, there are various types of angles you will get to study in Mathematics, but in this discussion, we will put the focus on reflex angles. So, let’s start!

What is a Reflex Angle?

A reflex angle stands always more than 180 degrees and smaller than 360 degrees.

A reflex angle can be presented as an interval with the help of the following units.

Measurement of a Reflex Angle

In general, when a student is given to measure an angle, the diagram will contain an arc drawn from the joining point. Students can evaluate the angle by directly using a protractor. But a protractor is marked up to 180 degrees, so how can you find a reflex angle?

First, recapitulate reflex angle meaning. In order to make a full 360 turn, an obtuse angle or an acute angle must be added to the reflex angle value.

So, if you are given an acute or obtuse angle measuring x, then full 360 degrees can be achieved with the following expression:

x + r = 360 degrees, here r is the reflex angle.

If the reflex angle is unknown, take ‘x’ on the right-hand side of the equation.

r = 360 – x

This expression is useful in finding out the value of the reflex angle when the obtuse or acute angle is known.

Therefore, when the corresponding obtuse or acute angle is not given, make use of a protractor to find it out. Further, subtract the value from 360 degrees to determine the measurement of a reflex angle.

Other Kinds of Angles

Like as we mentioned earlier about various types of angles, here we have listed the fundamental angles you will study in Mathematics:

As the name sounds, when an angle is nothing but 0 degrees, it is a zero angle.

When the angle is lesser than 9 degrees, it is denoted as an acute angle.

When the angle is greater than 90 degrees and less than 180 degrees, they are termed as obtuse angles.

An angle making 1/4th turn or 90 degrees is a right angle and the two lines forming the same are known as perpendicular, normal or orthogonal.

When an angle is making ½ turn, it is called a straight angle.

• Perigon or Complete Angle 

A full angle, or perigon or a complete angle makes 360 degrees turn.

Oblique angles have sides that are not perpendicular, which means the angle formed is not a right angle or a multiple of it.

Labelling Angles

Students can proceed with two ways to label angles. You can name the angle with a lower-case alphabet like a, b, c, d, etc., or you can use Greek letters like theta or alpha.

On the other hand, you can label an angle with three alphabets where the middle letter denotes the actual angle—for instance, ABC, BAC, CBA, etc.

Do It Yourself

Problem 1. Determine which of the following diagrams are reflex angles.

Problem 2. Find out which among the following angles is not a reflex angle?

(a) 182 degrees (b) 359 degrees (c) 270 degrees (d) 178 degrees

If you wish to gather more reflex angle information, please download the app today! We have a substantial amount of study materials and online tutorials that will assist you to score remarkably in exams.