Dilations are transformations that produce images that are the same shape as the original image, but not the same size. Two figures that have the same shape, but are different sizes are called similar. When two figures are similar, the ratios of the lengths of their corresponding sides are equal. The scale factor or dilation factor is the ratio of these corresponding sides. When the scale factor is greater than one, the image is called an enlargement and when the scale factor is less than one, the image is called a reduction.

In your words, what is the definition of dilation?

What is the difference between similar and congruent?

Consider the images below:

Using the toolbar find the measure of Side C' and Side C:

Now write them a ratio what did you get?

Is this an enlargement or reduction? Explain how you know from the ratio and how the images themselves prove it.

Use the toolbar to find the measure of A and A'. Are the measures of these angles congruent?

Use the toolbar below to enlarge and reduce the triangle below

Pick one of your dilations:

What was the scale factor? What were your new ordered pairs? What did you notice when you compare the ordered pairs of the pre-image with the ordered pairs of your image?

Self Assessment:

Check all that apply