A dilation is a type of transformation that either enlarges or reduces the size of a figure. For example, think about blowing up a round balloon. The balloon starts off small, but as you blow more air into it, the shape of the balloon dilates, or becomes larger. In a dilation, the image is not congruent to the pre-image. Because of this, dilations are not an isometry. You will investigate dilations of geometric figures both on and off the coordinate plane.

Essential Questions

• How can you determine if a figure has been dilated?
• How can you determine a dilation image?

 

Warm-Up

Did you know that the pupils of your eyes get larger or smaller depending on the amount of light in your environment? Actually, it is the muscles of your iris, the part of your eye that gives you your eye color, that contract and expand to change the size of your pupil, the dark circle in the center of your eye. When exposed to light, the pupil grows larger and is said to be dilated. In geometry, dilation is either a reduction or enlargement in size. You are about to extend the concept of dilation to geometric figures.