CCSS.Math.Content.HSG-CO.A.2
The standard
Represent transformations in the plane using, e.g., transparencies and geometry software; describe transformations as functions that take points in the plane as inputs and give other points as outputs. Compare transformations that preserve distance and angle to those that do not (e.g., translation versus horizontal stretch).
Common Core State Standards for Mathematics
What this standard means
Students need to show transformations on the coordinate plane and explain them as rules that move every point to a new point. They should use tracing paper, patty paper, graph paper, or dynamic geometry software to model translations, rotations, reflections, and stretches.
Mastery means students can predict image points, write simple function rules like (x, y) to (x + 3, y - 2), and decide whether distance and angle measure stay the same. Common trouble spots are mixing up x and y changes, describing only one point instead of the whole figure, and assuming every transformation keeps the shape congruent.
Ways to teach it
- Have students use patty paper to translate, rotate, reflect, and stretch a triangle on graph paper, then label each image point.
- Ask students to write which transformations keep a triangle congruent and explain their reasoning using side lengths and angle measures.
- Give three point rules and one triangle, then have students sketch each image and mark whether it preserves distance and angle.
- Show a photo resizing menu and compare dragging a corner proportionally with stretching only the width of the image.
Plan a lesson for CCSS.Math.Content.HSG-CO.A.2
Generate a complete lesson plan aligned to this standard, with objectives, activities, and materials. Free, no account needed.
Related standards
- CCSS.Math.Content.HSG-SRT.A.2
Given two figures, use the definition of similarity in terms of similarity transformations to decide if they are similar; explain using similarity transformatio...
- CCSS.Math.Content.HSG-CO.A.4
Develop definitions of rotations, reflections, and translations in terms of angles, circles, perpendicular lines, parallel lines, and line segments.
- CCSS.Math.Content.HSG-CO.A
Experiment with transformations in the plane
- 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. ...