Dilation Nation

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Objective

SWBAT identify and draw dilations on coordinate planes using polygons.

Big Idea

Students will review transformations using a brain pop and learn how to geometrically enlarge and shrink shapes.

Do Now and Review of Transformations

20 minutes

Do Now:  In this Do Now, students will review a composition of transformation with a reflection and translation. Teachers should try to emphasis that we always start with the second transformation first and then complete the first one.  This is an important skill for evaluating functions in a second year course of Algebra. 

 

Teachers can also review the agenda and objective for this lesson.

 

To start class, teachers will show a brain pop, which reviews transformations that have been studied so far in this unit.  Students with scaffolded notes can follow along and answer the following questions: 

1)   What are real-world examples of transformations?

2)   What 3 transformations have we learned so far? 

3)   Have you heard of the word dilation before? If so, where and when?

When reviewing these questions with students, teachers may want to bring up the idea of congruent shapes.   Since all of the transformations learned so far have preserved the pre-image figure’s size and shape, it might be a good time to hint at our new transformation (dilation), which does not preserve size.   I’ve included three photos of Beyonce to emphasis this for students. 

 

Teachers can review the definition of a dilation and connect this with prior knowledge about scale factors and similar figures.  There are also many notational ways to denote a dilation, I have included three examples on page 1 of notes.  It may be a good idea to check with your state assessments or upcoming CCSS exams to adjust this section accordingly.  The video link in the middle of the lesson will provide an overview on how to explain the Exploration.  

Class Notes and Dilation Practice

35 minutes

Activity/Homework and Exit Ticket

25 minutes

After reviewing composition of transformations with dilations, students can break into small groups or pairs to work on the attached review sheet.  This handout reviews a host of topics from transformations and teachers may want to collect this (to grade) or ask students to write and explain answers to the entire class.

The Exit Ticket for this lesson asks students take one point and dilate it by a factor of 3 and one-third.  Then, students are asked to review the rules for enlarging and shrinking a pre-image.