# 1.9: Constructions and Copying a Line Segment

**At Grade**Created by: CK-12

## Learning Objectives

- Define geometric construction
- Copy a given line segment using only a compass and a straightedge

## Introduction to Constructions: Compass and Straightedge

The word **construction** in geometry has a very specific meaning: the drawing of geometric items such as lines and circles using only a **compass** and **straightedge**. A **compass** is a drawing tool that can be used to measure distances and draw arcs and circles. An **arc** is a piece of a circle.

We make **constructions** in geometry using a **compass** and a _________________________.

**Compasses** come in different forms. These are some examples and drawings of compasses. You can also see an arc in the last two pictures:

A **straightedge** can be anything with straight edge, like an index card. The important thing to remember with constructions is that you are *not* allowed to measure angles with a protractor or measure lengths with a ruler.

## Construction: How to Copy a Line Segment

http://www.mathopenref.com/constcopysegment.html

**Reading Check:**

1. *Fill in the blank:* A construction is a geometric drawing made with only a ________________________________ and a __________________________________.

2. *Copy the line segment seen below using the steps you learned to make a construction. If you don’t have the tools to do it, write the steps you would take to copy it.*

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