Making the Moves
5 min
Teacher Prep
Setup
Narrative
In this Warm-up, students are asked to sketch a reflection of a given triangle and explain the strategies they used. The goal is to prompt students to notice and articulate that they can use the location of a single point and the fact that the image is a reflection of the triangle to sketch the image. To encourage students to use what they know about reflections and not count every grid line, flash the image for a few seconds and then hide it. Flash it once more for students to check their thinking.
Launch
Before beginning, make sure students have their books or devices open to the correct page. Tell students that an image of a reflection of triangle ABD will be shown for 3 seconds. Their job is to draw the image and explain any strategies they used.
Display the completed image for 3 seconds and then hide it. Do this twice. Give students 1 minute of quiet work time after each flash of the image. Encourage students to think about any shortcuts they used to draw the reflected image.
Student Task
Here is an incomplete image. Your teacher will display the completed image twice, for a few seconds each time. Your job is to complete the image on your copy.
Sample Response
Sample response: The first flash showed where to put B′ and the second flash where to put A′. Once these were in place, there was only one place D′ could go, underneath the segment A′B′, so that triangle A′B′D′ is a reflected image of triangle ABD.
Activity Synthesis (Teacher Notes)
Select a few students to share strategies they used in sketching their figure. Consider asking some of the following questions:
- "What was important in creating your sketch (what did you need)?"
- "What did you look for in the first flash? The second?"
- "What stayed the same and what is different in the shape and its image?"
- "How did you decide where to place the vertices of the image?"
- "How did you decide how long to make the sides?"
Anticipated Misconceptions
Students may struggle drawing the image under transformation from the quick flashes of the image because they are trying to count the number of spaces each vertex moves. Encourage these students to use the line in the image to help them reflect the image.
Standards
- 8.G.1·Verify experimentally the properties of rotations, reflections, and translations:
- 8.G.A.1·Verify experimentally the properties of rotations, reflections, and translations:
15 min
15 min
Knowledge Components
All skills for this lesson
No KCs tagged for this lesson
Making the Moves
5 min
Teacher Prep
Setup
Narrative
In this Warm-up, students are asked to sketch a reflection of a given triangle and explain the strategies they used. The goal is to prompt students to notice and articulate that they can use the location of a single point and the fact that the image is a reflection of the triangle to sketch the image. To encourage students to use what they know about reflections and not count every grid line, flash the image for a few seconds and then hide it. Flash it once more for students to check their thinking.
Launch
Before beginning, make sure students have their books or devices open to the correct page. Tell students that an image of a reflection of triangle ABD will be shown for 3 seconds. Their job is to draw the image and explain any strategies they used.
Display the completed image for 3 seconds and then hide it. Do this twice. Give students 1 minute of quiet work time after each flash of the image. Encourage students to think about any shortcuts they used to draw the reflected image.
Student Task
Here is an incomplete image. Your teacher will display the completed image twice, for a few seconds each time. Your job is to complete the image on your copy.
Sample Response
Sample response: The first flash showed where to put B′ and the second flash where to put A′. Once these were in place, there was only one place D′ could go, underneath the segment A′B′, so that triangle A′B′D′ is a reflected image of triangle ABD.
Activity Synthesis (Teacher Notes)
Select a few students to share strategies they used in sketching their figure. Consider asking some of the following questions:
- "What was important in creating your sketch (what did you need)?"
- "What did you look for in the first flash? The second?"
- "What stayed the same and what is different in the shape and its image?"
- "How did you decide where to place the vertices of the image?"
- "How did you decide how long to make the sides?"
Anticipated Misconceptions
Students may struggle drawing the image under transformation from the quick flashes of the image because they are trying to count the number of spaces each vertex moves. Encourage these students to use the line in the image to help them reflect the image.
Standards
- 8.G.1·Verify experimentally the properties of rotations, reflections, and translations:
- 8.G.A.1·Verify experimentally the properties of rotations, reflections, and translations: