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Unit 1 - Lesson 9 - Grade 8: Illustrative Mathematics

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20 Questions
Note from the author:
Grade 6 Unit 1
Lesson 9: Moves in Parallel
CC BY 2021 Illustrative Mathematics®
Grade 6 Unit 1
Lesson 9: Moves in Parallel
CC BY 2021 Illustrative Mathematics®
Lesson: Moves in Parallel

Line Moves (Warm Up)

1.

Describe a translation, rotation, or reflection that takes line ℓ to line ℓ'.

2.

Plot and label A' and B', the images of A and B.

3.

Describe a translation, rotation, or reflection that takes line ℓ to line ℓ'.

4.

Plot and label A' and B', the images of A and B.

Parallel Lines

Use a piece of tracing paper to trace lines a and b and point K. Then use that tracing paper to draw the images of the lines under the three different transformations listed.

As you perform each transformation, think about the question:

What is the image of two parallel lines under a rigid transformation?
5.

Translate lines a and b 3 units up and 2 units to the right.

What do you notice about the changes that occur to lines a and b after the translation?

6.

What is the same in the original and the image?

7.

Rotate lines a and b counterclockwise 180 degrees using K as the center of rotation.

What do you notice about the changes that occur to lines a and b after the rotation?

8.

What is the same in the original and the image?

9.

Reflect lines a and b across line h.

What do you notice about the changes that occur to lines a and b after the reflection?

10.

What do you notice about the changes that occur to lines a and b after the reflection?

11.

What is the same in the original and the image?

Let’s Do Some 180’s

The diagram shows a line with points labeled A, C, D, and B.
12.

On the diagram, draw the image of the line and points A, C, and B after the line has been rotated 180 degrees around point D.

13.

Label the images of the points A', B', and C'.

14.

What is the order of all seven points? Explain or show your reasoning.

The diagram shows a line with points A and C on the line and a segment AD where D is not on the line.
15.

Rotate the figure 180 degrees about point C. Label the image of A as A'and the image of D as D'.

16.

What do you know about the relationship between angle CAD and angle CA'D'? Explain or show your reasoning.

The diagram shows two lines ℓ and m that intersect at a point O with point A on ℓ and point D on m.
17.

Rotate the figure 180 degrees around O. Label the image of A as A' and the image of D as D'.

18.

What do you know about the relationship between the angles in the figure? Explain or show your reasoning.

Cool Down: Finding Missing Measurements

Finding Missing Measurements

Points A', B', and C' are the images of 180-degree rotations of A, B, and C, respectively, around point O.
Answer each question and explain your reasoning without measuring segments or angles.
19.

Name a segment whose length is the same as segment AO.

20.

What is the measure of angle A'OB'?