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# Constructing Quadrilaterals using Geometer's Sketchpad

Lesson 9 of 13

## Objective: SWBAT use Geometer's Sketchpad to construct various quadrilaterals

#### Do Now

*5 min*

Using prior knowledge, students define the following words: quadrilateral, parallelogram, rectangle, and square.

Students need to know the definitions of these words for the activity. I use very basic definitions, ie. a quadrilateral is a polygon with four sides, a parallelogram is a quadrilateral with two sets of parallel sides, a rectangle is a parallelogram with four right angles, and a square is a rectangle with four congruent sides. For the purpose of the activity, it is not necessary to talk about rhombuses and trapezoids. They will be addressed in later lessons.

As the students are working, I hand out the laptops needed for the lesson.

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#### Mini-Lesson

*10 min*

We start the Mini-Lesson by reviewing the terms from the "do now." In addition to those terms, we review the definitions of parallel and perpendicular lines. All though students have heard these terms many times, they often need a refresher of the definitions.

Students open up the program Geometer's Sketchpad and we review how to construct parallel and perpendicular lines. We also go over how to measure the angle formed by the intersection of two perpendicular lines.

Before students begin the lesson activity, we explore deleting and hiding points and lines. Sometimes when students delete unwanted parts, they delete wanted parts, as well. The "hide" tool only affects the highlighted parts.

Hint: Mac: To hide a part press command + h and to delete a part press command + z.

PC: To hide a part press ctrl + h and to delete a part press ctrl + z.

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#### Activity

*30 min*

Students construct various quadrilaterals independently based on the definitions discussed in the Mini-Lesson.

The most common error students make is by drawing "parallel" and "perpendicular" lines instead of constructing them. As I circulate, I check to see if the figures pass the "Drag Test." For the "Drag Test," I drag a point or side of the figure. If the figure changes shape, it doesn't pass the "Drag Test." I then remind students about the difference between constructing and drawing.

Students who finish the basic constructions and answer the questions can explore the program more by adding text and measuring different parts of their figures. Students can play around with the document options to add extra pages or with the Animate button to see what happens.

*I always keep some extra self-guided tours for students who work quickly and correctly. See the website www.dynamicgeometry.com.

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#### Summary

*5 min*

**Exit Ticket: **How does constructing a square differ from constructing a rectangle?

As the students answer the question, I collect their laptops.

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- UNIT 1: Preparing for the Geometry Course
- UNIT 2: Geometric Constructions
- UNIT 3: Transformational Geometry
- UNIT 4: Rigid Motions
- UNIT 5: Fall Interim Assessment: Geometry Intro, Constructions and Rigid Motion
- UNIT 6: Introduction to Geometric Proofs
- UNIT 7: Proofs about Triangles
- UNIT 8: Common Core Geometry Midcourse Assessment
- UNIT 9: Proofs about Parallelograms
- UNIT 10: Similarity in Triangles
- UNIT 11: Geometric Trigonometry
- UNIT 12: The Third Dimension
- UNIT 13: Geometric Modeling
- UNIT 14: Final Assessment

- LESSON 1: What is Geometry?
- LESSON 2: Geometric Terms
- LESSON 3: What are Geometric Constructions?
- LESSON 4: Bisecting Angles
- LESSON 5: Constructing Parallel Lines
- LESSON 6: Constructing Triangles
- LESSON 7: Constructing Inscribed Regular Triangles, Quadrilaterals and Hexagons
- LESSON 8: Introduction to Constructions with Geometer's Sketchpad
- LESSON 9: Constructing Quadrilaterals using Geometer's Sketchpad
- LESSON 10: Constructing Regular Polygons Inscribed in Circles using Geometer's Sketchpad
- LESSON 11: Geometric Construction Review
- LESSON 12: Geometric Constructions End of Unit Assessment
- LESSON 13: Geometric Constructions Assessment Error Analysis