Reflections 2

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Objective

SWBAT understand reflection across any horizontal or vertical line.

Big Idea

Can you reflect objects without the geomirrors? Push kids to apply the idea of equal distance from the line of reflection.

Lesson Author

Jeff Li MTP

New York, NY

Grade Level

Eighth grade

Subjects

Math

Geometry

Standards

8.G.A.1

Verify experimentally the properties of rotations, reflections, and translations:

8.G.A.1a

Lines are taken to lines, and line segments to line segments of the same length.

8.G.A.1b

Angles are taken to angles of the same measure.

8.G.A.1c

Parallel lines are taken to parallel lines

8.G.A.2

Understand that a two-dimensional figure is congruent to another if the second can be obtained from the first by a sequence of rotations, reflections, and translations; given two congruent figures, describe a sequence that exhibits the congruence between them.

8.G.A.3

Describe the effect of dilations, translations, rotations and reflections on two-dimensional figures using coordinates.

8.G.A.4

Understand that a two-dimensional figure is similar to another if the second can be obtained from the first by a sequence of rotations, reflections, translations, and dilations; given two similar two-dimensional figures, describe a sequence that exhibits the similarity between them.

MP1

Make sense of problems and persevere in solving them.

MP3

Construct viable arguments and critique the reasoning of others.

Warm Up

10 minutes

Each day, students complete a warm-up that usually consists of spiraling the previous day's material, in addition to older material. Warm-up problems also sometimes extend lessons that students have encountered before to more unfamiliar contexts.

For a video narrative about how I structure each lesson, and how the warm-up fits in, click here.

Play of the Day

40 minutes

Huddle

10 minutes

I like to review Problem #3 during the huddle, to shine a light on what happens when the line of reflection actually cuts through the shape to be reflected. What does this look like with the Geomirror? Basically, it flips it around, but if you very precisely apply the idea of equal distance from the line of reflection, it yields the shape. It's a pretty cool demonstration of how applying the properties here yields a precise reflection.