Reflections 3

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Objective

SWBAT understand reflection across the lines y = x and y = -x.

Big Idea

Push students' understanding of reflections by reflecting across diagonal lines. Tricky!!!! (and some cool patterns emerge).

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.

MP2

Reason abstractly and quantitatively.

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

For the huddle, I like to review #4, #5, and #6, because they are asking questions that do not have a diagram. For some kids, they apply the abstract rules of a reflection across y=x, but I encourage all the kids to sketch their own visuals for this... which is really powerful for anything involving geometry.

We practice this sketch for all three examples, and I spiral this strategy for the next few days, pretty diligently.