6.3.1 Use similar Polygons Chapter 6: Similarity

Similar Polygons Two polygons are similar if Corresponding Angles are congruent Corresponding sides are proportional Scale factor  ABC ~  DEF (triangle ABC is similar to trangle DEF) AB C DF E

Investigation In the figure is  ABC ~  DEF? Find the scale factor AB C DF E = ? = ? = ? = ?

Using the Scale factor In the figure  ABC ~  DEF Find the value of x The scale factor is the ratio I will use it to define a proportion AB C DF E 21 x Cross multiply to solve:

Perimeters of similar figures If two polygons are similar, then the ratio of their perimeters is equal to the ratios of their corresponding sides (it is the scale factor) These two polygons are similar, find the perimeters and compare the scale factor is 35:7 or 60:12 which both reduce to 5:1 The scale factor of the perimeters and the sides is the same What about area? Think about the units of measure

Homework p , 3, 6, 7, 10, 19, 20, 31, 34