# 180 degree angle

180 degree angle
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In this mini-lesson, we will learn about 180-degree angles. While doing so we will also discuss creating a 180-degree angle with a compass, and steps to be followed to construct a 180-degree angle. You can check out the interactive simulations to know more about the lesson and try your hand at solving a few interesting practice questions at the end of the page.

Before we get started, have you ever noticed the angle between the two hands of a clock when at 6 o'clock? The angle between the two hands of the clock above is 180° because it forms a straight line.

Let us explore more about the 180° angle.

## Lesson Plan

 1 What is 180-Degree Angle? 2 Thinking out of the Box! 3 Solved Examples on 180-Degree Angle 4 Important Notes on 180-Degree Angle 5 Interactive Questions on 180-Degree Angle

## What Is 180 Degree Angle?

We know that an angle is formed when two rays meet at a vertex. If the angle formed at the vertex O measures 180°, we call it a 180-degree angle.

A straight angle is called a 180-degree angle.

It is also called a half-circle. It looks like a straight line. ## How to Construct 180-Degree Angle Using a Protractor?

In this section, let us explore how to construct a 180-degree angle with the help of a protractor.

• Step 1: Draw a line segment $$OA$$
• Step 2: Place the protractor at the point $$O$$
• Step 3: In the outer circle of the protractor look for 180° reading and with a pencil mark a dot and name it $$C$$
• Step 4: Join $$O$$ and $$C$$. Now,  $$\angle AOC =180 ^\circ$$

Still, confused? Look at the simulation below.

Click on the "Go" button to understand the process of construction of a 180-degree angle using a protractor.

## What Are 180-degree Angles in Real Life?

180° angles are widely seen in real life.

In everyday life, 180-degree angles are used. For constructing structures, highways, houses, and sports facilities, engineers and architects use angles. Carpenters make benches, tables, and sofas using angles. Observe where you can see 180° angles in your surrounding areas. Think Tank
• How many 180-degree angles are there in a complete angle?

## Solved Examples

 Example 1

Can you help Alex find out the difference between a 180° angle and a 90° angle?

Solution

The 180-degree angle is a straight line, known as a semi-circle.

A 90-degree angle is a quadrant or one-fourth of a circle.

 180-degree is a straight line or semicircle and 90 degree is a quadrant
 Example 2

Alina wants to construct a 180° angle using a protractor. Can you help her construct?

Solution

Step 1: Draw a ray (part of a line that has a vertex at one end and an arrowhead at another). Mark the vertex as point O.

Step 2: Point O denotes the vertex of the angle.

Step 3: Now put the protractor above the point O vertex and match the baseline of the protractor along with the arm of the angle.

Step 4: Mark the angle 180 degrees with a dot.

Step 5: Now join this new vertex with point O. This forms another arm of the angle.

Now, we get a straight angle. More Important Topics
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