CCSS.Math.Content.HSG-CO.A
The standard
Experiment with transformations in the plane
Common Core State Standards for Mathematics · High School — Geometry
What this standard means
Students need to move figures on a coordinate plane and notice what changes and what stays the same. They should try translations, rotations, reflections, and dilations, then describe each move using clear language, coordinates, and diagrams.
Mastery looks like a student predicting the image of a point or shape, checking it, and explaining the rule used. Students often mix up rotation direction, reflect over the wrong line, or describe a move too vaguely, like saying “it flipped” without naming the line of reflection.
Ways to teach it
- Give students patty paper and a coordinate grid, then have them physically translate, rotate, and reflect a triangle to match target images.
- Ask students to write directions for moving one figure onto another so a classmate can recreate the transformation exactly.
- Show three transformed points and ask students to name the transformation rule, then check with one more point.
- Have students analyze a phone photo edit, crop, rotate, mirror, or resize, and identify the transformations used.
Plan a lesson for CCSS.Math.Content.HSG-CO.A
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Related standards
- CCSS.Math.Content.HSG-CO.A.2
Represent transformations in the plane using, e.g., transparencies and geometry software; describe transformations as functions that take points in the plane as...
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(+) Work with 2 × 2 matrices as transformations of the plane, and interpret the absolute value of the determinant in terms of area.
- CCSS.Math.Content.HSG-CO.A.5
Given a geometric figure and a rotation, reflection, or translation, draw the transformed figure using, e.g., graph paper, tracing paper, or geometry software. ...
- CCSS.Math.Content.8.G.A.1
Verify experimentally the properties of rotations, reflections, and translations: