Transforming Similar Shapes

Similarity and Transformations

Lesson 9.3

Poll

Which figure is the preimage and how do you know?

• Green, because it is most to the left

• Blue, because it is the smallest

• Orange, because it has prime markers on the corners.

• Blue because the corners are marked EFGH (no prime markers)

Poll

Since the blue figure is the preimage, which figure is the FIRST in the sequence?

• Green, because it is has 1 prime marker on each corner.

• Orange, because it has 2 prime markers on each corners.

Poll

Since the green figure is the FIRST in the sequence, by what scale factor was it enlarged?

• +2

• *2

When you have figures that are enlarged or shrunk, you can find the scale factor by comparing corresponding sides. Remember that scale factors are multiplied, not added.

Similar

• Figures that have the same shape but necessarily the same size.

• If one image can be obtained from another by a sequence of transformations and dilations

Are these two figures similar?

p. 502 Complete the ratios of the side lengths in step 1. Since the ratios are equal, a dilation with a scale factor of 2 is one of the transformation that maps DEF onto GHI

Are these figures similar?

p. 504 You write the ratios to determine if all the sides are proportional.

These figures are not similar

The ratios are not equivalent.

Dilations and scale factor

p. 505

These figures are similar.

Find the scale factor. p. 505

Original photo is 2 in by 3 in

9.3 p. 511 in WB on reveal: #1-4, 6 and 9 (BONUS: 5, 7 and 8)