NY Next Generation Math NY-8.G.3

Math8th GradeUnderstand congruence and similarity using physical models, transparencies, or geometry software.

The Standard

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

New York State Next Generation Mathematics Learning Standards

Teacher's field guide

What Students Need to Do: Students describe how dilations, translations, rotations, and reflections change coordinates of two-dimensional figures. They use permitted coordinate rules to determine image vertices.
What Mastery Looks Like: The student applies translations, dilations, reflections across x = k or y = k, and 90- or 180-degree rotations about the origin. Coordinates and transformation descriptions agree.
Common Misconceptions: Students may change only one vertex or apply coordinate rules inconsistently. They may rotate clockwise when no direction is given or reflect across the wrong line.
How to Assess It: Give triangle vertices and ask for images after reflection across x = 1 and a 90-degree counterclockwise rotation about the origin. Require coordinate rules.

Lesson moves

Trace a coordinate figure on transparencies and perform a specified reflection, rotation, translation, and dilation.
Ask students which coordinates change under a translation compared with a dilation centered at the origin.
Play Transformation Rule Match with coordinate figures and image-vertex cards.
Describe coordinate changes when resizing and repositioning a floor-plan shape on a grid.

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