Dilation and Similarity

Dilation and Similarity

Changing size not shape

Line Dilations

When lines are dilated, then lines are parallel.

Poll

If line AB is dilated to form line A'B', what is true about the two lines?

• The lines are perpendicular.

• The lines are parallel.

• The lines intersect.

Line Dilations

When lines are dilated, the length of the image or new line is larger or smaller by the scale factor. Multiply the length of the original line by the scale factor.

Poll

Line AB is dilated by a factor 3.5 to form line A'B'. If the length of segment AB is 5 inches, what is the length of of segment A'B' ?

• 8.5 inches

• 17.5 inches

• 1.4 inches

Similar Figures

Similar figures have the same shape, but a different size.

Similar Figures

Similar Polygons

Corresponding sides of similar figures must be proportional or multiplied by the same scale factor. 5 times 2 equals 10. The scale factor is 2.

Poll

What are the corresponding angles?

• $$\angle A\ and\ \ \angle D$$

• $$\angle B\ and\ \angle D$$

• $$\angle A\ and\ \angle F$$

• $$\angle C\ and\ \angle F$$

• $$\angle B\ and\ \angle E$$

Poll

What are the corresponding sides?

• $$\overline{AB}\ and\ \overline{EF}$$

• $$\overline{BC}\ and\ \overline{EF}$$

• $$\overline{BC}\ and\ \overline{DE}$$

• $$\overline{AB}\ and\ \overline{DE}$$

• $$\overline{CA}\ and\ \overline{FD}$$