## Constructing a Bisector - Section 2: Constucting a Bisector

# Going Halvesies

Lesson 9 of 14

## Objective: 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.

#### Lesson Opener

*5 min*

**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.

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#### Constucting a Bisector

*10 min*

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.

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#### Practice & Investigation

*20 min*

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.

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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.

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**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.

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- UNIT 1: Models and Constructions
- UNIT 2: Dimension and Structure
- UNIT 3: Congruence and Rigid Motions
- UNIT 4: Triangles and Congruence
- UNIT 5: Area Relationships
- UNIT 6: Scaling Up- Dilations, Similarity and Proportional Relationships
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- LESSON 1: Welcome to Geometry!
- LESSON 2: Preview and Goal-Setting
- LESSON 3: Mystery of the Nazca Lines
- LESSON 4: Cell Phone Towers
- LESSON 5: Cell Phone 9-1-1
- LESSON 6: Submarine Smart Phone
- LESSON 7: Reviewing Geometric Models
- LESSON 8: Introduction to Constructions
- LESSON 9: Going Halvesies
- LESSON 10: Inventory Testing
- LESSON 11: Flexing Our Bisectors
- LESSON 12: Finding Your Center
- LESSON 13: Reviewing Constructions
- LESSON 14: Models & Constructions Unit Quiz