Lesson 1: 7-1: Dilations

1. Given a center and scale factor, how do you draw a dilation?
2. If you have dilated a figure to 3 times its original size, what do you know about the lengths of the sides compared to its original?
3. Does the location of the center of dilation change the shape of the dilated image?

Dilation
Scale Factor

G.CO.2
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).

A dilation is a transformation that changes the size of a figure by a scale factor. If the scale factor is 1, then the dilation is a congruence transformation transformation. If the scale factor is not 1, then the dilation is a similarity transformation.

Charles can resize his photos before uploading them to a social networking site. Scaling down the size or enlarging the size of the original photo is an example of a dilation.

Be sure not measure beyond the center of dilation. The scale factor is to be measured beginning at the center of dilation.

Students approaching grade level can be given practice problems in small groups to work with other students or directly with the teacher.
Students beyond grade level can make deeper connections by performing a composition of dilations with two different centers.

Formative Assessment

Textbook in class

Access online textbook and resources through class link.