[Maths Class Notes] on How To Draw 180 Degree Angle Pdf for Exam

Angles are measured in degrees (or radians), and there are many types of angles in geometry; acute, obtuse, right angle, half a circle, full rotation, etc. A full circle is 360 degrees, and all angles lie within that. 

An angle that measures exactly 180 degrees is called a straight angle. Another 180-degree angle name is half a circle. If a straight line is split into two and we know one angle, we can always calculate the other since a straight line is always 180 degrees, so the sum of the angles would be 180 degrees. 

In radians, a 180-degree angle is represented as π (pi). 

You can find a 180-degree angle picture below:

In this article, we will see the details of 180 angles and how to draw 180-degree angles.

Types of Angles

Let us take a quick at all possible types of angles that can exist within a circle and their measurements. 

Any angle that is more than 0 degrees and less than 90 degrees is an acute angle.

Right angle is 90 degrees exactly.

Any angle that is more than 90 degrees and less than 180 degrees is an obtuse angle.

Straight angle is 180 degrees exactly.

An angle that is more than 180 degrees and less than a full revolution or 360 degrees is a reflex angle. 

Full rotation is 360 degrees exactly.

You can easily find all the angles in one place in the diagram below:

Steps of Construction of 180 Degree Angle

To construct any angle we would need two things:

Before we tell you how to draw a 180-degree angle, let us familiarize ourselves with the basics of a compass.

A compass is a tool that helps in finding directions. It has a magnetic needle that always points at the magnetic north. One can find the direction by the angle that the desired object direction and the magnetic needle make.

We will now look into the steps of construction of 180-degree angle:

• Draw a straight line l, using a ruler

• Mark a point “O” anywhere on the line l.

• The angle BOA is the straight angle or 180 degrees.

• You can verify if it is a 180 angle or not, by using a protractor. Keep the protractor at the top of the point O and then measure the angle BOA. It should show as 180 degrees.

Examples of Straight Angle

You notice many straight lines in your day to day lives, some common examples are:

• A flat surface – This has an angle of 180 degrees.

• A see-saw is a straight angle example.

• A stick is 180 degrees at the centre.

Straight line and straight angle are not the same. The straight angle measures 180 degrees and a straight line connects the two points.

Straight Angle Theorem

As per the straight angle theorem, all straight angles represent 180 degrees. In an angle, if its legs are pointing in exactly opposite directions, it forms a straight or 180 angle. The line segment in geometry is a good example of a straight angle as its endpoints extend in opposite directions.

Straight Angle Properties

We have listed here a few key properties of a straight angle:

• A straight angle is a measure of half of a revolution.

• We can produce a straight angle by revolving one ray of a line segment by exactly 180 degrees with respect to the other ray.

• The arms of a straight angle extend in opposite directions.

• A straight angle modifies the direction of a point.

• You can get a straight angle by joining two right angles.

Positive and Negative Angles

Starting from a line, there are two ways you can measure the angle: clockwise and anticlockwise. 

The direction of a positive angle is counterclockwise i.e. opposite to the direction in which a clock goes.

This is measured clockwise.

When you are measuring and naming an angle to be sure of which angle you have been asked for and measure it counter-clockwise (positive angle)

In the figure above, the smaller angle is obtuse while the bigger one is a reflex angle.