Presentation on theme: "7-2 Similar Polygons Objective To identify and apply similar polygons."— Presentation transcript:
7-2 Similar Polygons Objective To identify and apply similar polygons
Similar Figures: same shape but not necessarily the same size Abbreviate is similar to with the symbol. ~ You can use ratios and proportions to decide whether two polygons are similar and to find unknown side lengths of similar figures.
Similar Polygons: And Corresponding sides are proportional. Notation: ∆ABC ~ ∆DEF Similar Polygons: And Corresponding sides are proportional. Notation: ∆ABC ~ ∆DEF Corresponding angles are congruent
When three or more ratios are equal, you can write an extended proportion: Extended Proportion
Scale Factor Ratio of corresponding linear measurements of two similar figures The ratio of corresponding sides: simplify
What are the pairs of congruent angles? What is the extended proportion for the ratios of corresponding sides? You give it a shot.
Are the polygons similar? If so, write a similarity statement and give the scale factor. Pairs of congruent angles: Compare the ratios of corresponding sides: Corresponding sides are not proportional, so the polygons are not similar.
Similar Polygons: corresponding angles are congruent AND corresponding sides are proportional Does the AND matter? 12 cm 18 cm 10 cm Congruent Angles Yes Proportional sides No 12 cm Congruent Angles No 18 cm 50 0 130 0 50 0 Proportional sides Yes
Similar Polygon Problems Given: ABCDE ~ JKLMN Find x and y A B C D E 10 12 x J K L M N 15 y 9 = = 10 9 x 15 y 12 x = 6 y = 18
p. 444: 9-19 odd (include all ratios & diagrams)