Line Segments

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Objective

SWBAT create and interpret geometric notation and diagrams involving line segments and their measures; SWBAT measure line segments and construct line segments to specifications

Big Idea

A picture is worth a thousand words, and symbols are worth 500 or so. In this lesson, students learn the value of geometric diagrams and notation and they learn the importance of precision when creating notation and diagrams.

Lesson Author

Anthony Carruthers

Pasadena, CA

Grade Level

Ninth grade

Tenth grade

Subjects

Math

Standards

HSG-CO.A.1

Know precise definitions of angle, circle, perpendicular line, parallel line, and line segment, based on the undefined notions of point, line, distance along a line, and distance around a circular arc.

MP5

Use appropriate tools strategically.

Activate Prior Knowledge

10 minutes

Activating Prior Knowledge_Line Segments.docx page 1

Direct Instruction

30 minutes

Demanding precision from the start

Direct Instruction_Line Segments.docx page 1

Measurement and Construction

20 minutes

An overarching goal for this course is to impress upon students that, while Geometry is a very abstract subject, we have tools that allow us to make very concrete measurements involving geometric concepts. In this section of the lesson, students learn to use a ruler to measure segments. In my experience, it is a mistake to assume that students already know how to do this.

I start with an introduction to the markings on the ruler. I start with the metric side of the ruler since it is somewhat easier to understand for a novice. Next I model measuring lengths using a ruler. I do this on the document camera so that students can see clearly what I am doing.

Next I hand out the resource: Measuring and Creating Segments. As students work on the exercise, I circulate around the room playing the role of questioner/facilitator.

The types of questions I ask:

1. What do the directions say?

2. What information is given here?

3. Have you been as precise as possible in making your measurement?

4. How could you express in geometric notation that the length of the segment is.............cm?

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