Virginia SOL 8.MG.3.e
The Standard
Sketch the image of a polygon that has been reflected over the x- or y-axis.
Virginia Standards of Learning for Mathematics · The student will apply translations and reflections to polygons in the coordinate plane.
Teacher's field guide
What This Standard Means
What Students Need to Do
- Students plot a polygon's vertices and locate their mirror points across the x-axis or y-axis. They connect the new points in order and label the image.
What Mastery Looks Like
- Students correctly use (x, y) to (x, -y) for the x-axis and (x, y) to (-x, y) for the y-axis. Their image keeps the same size, shape, and distance from the axis.
Common Misconceptions
- Students may change the wrong coordinate, change both signs, or swap the coordinates. They may also plot the correct vertices but connect them in the wrong order.
How to Assess It
- Exit ticket: Plot triangle A(2, 1), B(5, 1), and C(3, 4), reflect it across the y-axis, then list the new coordinates.
Lesson moves
Ways to Teach It
Have students draw a polygon on a transparent coordinate grid, fold along one axis, and trace its reflected image.
Ask students to explain why reflecting across the y-axis changes x-coordinates but not y-coordinates.
Run a reflection relay where teams draw coordinate cards, plot each polygon, and reflect it across the named axis.
Give students half of a simple logo on a coordinate grid and have them complete its mirror image.
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Related Standards
- 8.MG.3.d
Sketch the image of a polygon that has been translated vertically, horizontally, or a combination of both.
- 8.MG.3.b
Given a preimage in the coordinate plane, identify the coordinates of the image of a polygon that has been reflected over the x- or y-axis
- 8.MG.3.f
Sketch the image of a polygon that has been translated and reflected over the x- or y-axis, or reflected over the x- or y-axis and then translated.
- 8.MG.3.c
Given a preimage in the coordinate plane, identify the coordinates of the image of a polygon that has been translated and reflected over the x- or y-axis or ref...
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