Flexing Our Bisectors

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Objective

SWBAT use dynamic geometry software to construct a (segment) bisector and verify its properties. Students will understand how learning constructions helps them to understand the properties of geometric objects.

Big Idea

What are the properties of a bisector? Students see for themselves--and learn the advantages of dynamic geometry software.

Lesson Author

Tom Chandler

Ault, CO

Grade Level

Tenth grade

Subjects

Math

Geometry

Geometric Modeling

Standards

HSG-CO.D.12

Make formal geometric constructions with a variety of tools and methods (compass and straightedge, string, reflective devices, paper folding, dynamic geometric software, etc.). Copying a segment; copying an angle; bisecting a segment; bisecting an angle; constructing perpendicular lines, including the perpendicular bisector of a line segment; and constructing a line parallel to a given line through a point not on the line.

MP5

Use appropriate tools strategically.

Lesson Opener

5 minutes

Team Warm-up

The Warm-Up prompt is a leading question: I ask students to consider the limitations of pencil-and-paper constructions, so that I can point out the advantages of dynamic geometry software.

This lesson opener follows our Team Warm-up routine, with students writing individual answers in their Learning Journals. I display the prompt using the Slideshow for the lesson.

Goal-Setting

Displaying the lesson Agenda and Learning Targets, I tell the class that today we will learn how to use dynamic geometry software to construct a bisector and investigate its properties. The software allows us to construct a figure, then move its vertices or change some of its measurements to see how this effects the figure.

The application we will be using is a freeware program called WinGeom.

Bisector Investigation

45 minutes

Using the Bisector Investigation to Check for Understanding

Lesson Close and Homework

4 minutes

Team Size-Up

The lesson close follows our Team Size-Up routine. The Lesson Close prompt asks students to name some of the advantages of dynamic geometry software.

Homework

Homework Set 2 problem #28 gives students another chance to use constructions to examine the properties of bisectors. Problem #29 provides practice with vocabulary and geometric notation. In Problem #30, students follow instructions (written using geometric vocabulary and notation) to construct an equilateral triangle inscribed in a circle.