How it works
This transformations graphic organizer sets the four moves side by side, so the difference that matters shows: three of them keep a figure's size and shape, and one can change its size.
Read the full guide
Draw what each move needs
A translation needs a distance and a direction. A reflection needs a line. A rotation needs a center and an angle, and a dilation needs a center and a scale factor. Have students draw these into the sketch itself: an arrow for the slide, the mirror line, a dot for the center.
Congruent or similar
In the Common Core standards for 8th grade, two figures are congruent when a sequence of rotations, reflections and translations takes one to the other. Put a dilation in the sequence and they are similar. The sheet for two moves in a row ends on that question.
- Label the image with prime marks: A goes to A′ and B to B′. It shows which corner went where.
- A scale factor greater than 1 enlarges a figure. A scale factor between 0 and 1 shrinks it.
Questions and answers
What are the four types of transformations?
Translation, reflection, rotation and dilation. A translation slides a figure, a reflection flips it over a line, a rotation turns it about a point, and a dilation enlarges or shrinks it from a center.
What is a rigid transformation?
One that keeps the distance between every pair of points, so a figure keeps its size and shape. Translations, reflections and rotations are rigid. A dilation that enlarges or shrinks a figure is not.
What is the rule for a 90 degree rotation?
Turning counterclockwise about the origin, the point (x, y) goes to (−y, x), so (2, 3) goes to (−3, 2). Clockwise, it goes to (y, −x). A 180° rotation sends (x, y) to (−x, −y) either way.
What grade are transformations taught?
In the Common Core standards they are 8th grade geometry: students verify the properties of rotations, reflections and translations, and describe the effect of all four on figures using coordinates. They return in high school geometry.