NY Next Generation Math NY-8.G.1.a

Math8th GradeVerify experimentally the properties of rotations, reflections, and translations.

The Standard

Verify experimentally lines are mapped to lines, and line segments to line segments of the same length.

New York State Next Generation Mathematics Learning Standards

Teacher's field guide

What Students Need to Do: Students rotate, reflect, or translate lines and line segments and observe the images. They use measurements or overlays to verify that lines remain lines and segment lengths stay unchanged.
What Mastery Looks Like: A student transforms a segment with tracing paper or geometry software and measures matching lengths before and after. The student also verifies that several points from one line map to points on another line.
Common Misconceptions: Students may stretch a segment during a transformation or compare horizontal and vertical changes instead of total length. They may also confuse an infinite line with a segment that has endpoints.
How to Assess It: Give students a drawn segment and a specified reflection. Ask them to create the image, measure both segments, and explain how the result verifies the property.

Lesson moves

Trace a line segment on transparent paper, rotate or reflect it, and measure the original and image with a ruler.
Ask students how three transformed points can help verify that the image of a line is still a line.
Play transformation match by pairing original segments with valid images that preserve length under a named movement.
Inspect a reflected or translated logo and verify that one straight edge keeps its length in the image.

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