# What is Rigid?

## What is Rigid?

UNIT 1 • LESSON 1 MOVING IN THE PLANEWHAT YOU WILL LEARNIn this lesson, I will describe ways figures can move in the plane.I can...
• Describe a translation, rotation, or reflection in the plane in one’s own words.
I will know I learned by...
• Demonstrating that I can describe how a figure moves and turns to get from one position to another.
FAMILY MATERIALS:To review or build a deeper understanding of the math concepts, skills, and practices in this lesson, visit the Family Materials provided by Illustrative Mathematics Open-Up Resources. (Links to an external site.)Links to an external site.Which one doesn’t belong?   Your teacher will give you three pictures. Each shows a different set of dance moves.
1. Arrange the three pictures so one of you can see them right way up. Choose who will start the game.
• The starting player chooses one of the three applets below and describes the dance to the other player.
• The other player identifies which dance is being talked about: A, B, or C.
2. After one round, trade roles. When you have described all three dances, come to an agreement on the words you use to describe the moves in each dance.
3. With your partner, write a description of the moves in each dance.
Dance A: Geogebra Applet (Links to an external site.)Links to an external site.Dance B: Geogebra Applet (Links to an external site.)Links to an external site.Dance C: Geogebra Applet (Links to an external site.)Links to an external site.We could think of each dance as a new dance by running it in reverse, starting in the 6th frame and working backwards to the first.
1. Pick a dance and describe in words one of these reversed dances.
2. How do the directions for running your dance in the forward direction and the reverse direction compare?
Here are two ways for changing the position of a figure in a plane without changing its shape or size:Sliding or shifting the figure without turning it. Shifting Figure A to the right and up puts it in the position of Figure B.Turning or rotating the figure around a point. Figure A is rotated around the bottom vertex to create Figure C.