SWBAT use straight-edge and compass to construct a (segment) bisector and verify its properties. Students will understand how geometric objects may be defined in terms of other objects and identified using geometric notation.

What are the properties of a bisector? Students see for themselves--and find that a compass is an efficient instrument for comparing distances.

5 minutes

**Team Warm-up**

The Warm-Up prompt for the lesson asks students to recall the properties of bisectors.

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 construct a bisector and to use constructions to investigate their properties.

10 minutes

As in the previous lesson, I use Guided Notes to demonstrate the construction of a bisector. Students complete the illustrations in their notes as they follow along.

I demonstrate the Construction of a Bisector in this video.

20 minutes

I display the instructions and distribute the activity. The goal is for students to practice the construction of a bisector and to use constructions to verify their properties.

This activity uses the Rally Coach format.

15 minutes

I ask students to get out their Guided Notes: Constructions/ Defining Geometric Objects. Now that we know what lines and circles are, we can define other objects--segments, rays, and arcs--with precision (**MP6**). We complete the final page of the notes: Defining Geometric Objects.

Displaying the guided notes with the help of an interactive whiteboard, I lead the class in completing the definitions and the examples. I encourage students to use straight-edge and compass to construct the diagrams, although this is not strictly necessary.

4 minutes

**Team Size-Up**

The lesson close follows our Team Size-Up routine. The prompt asks students to explain what constructions are and why we learn them. This essential question for the unit was answered in the notes.

**Homework**

Homework Set 2 problem #23 asks students to practice some of the constructions they have just learned. Problem #24 reviews algebra concepts (slope). In addition, I assign Portfolio Problem 2- Placing a Call, which students should now be able to answer completely.