1. S IMILAR P OLYGONS

2. Warm Up 1. If ∆ QRS  ∆ ZYX, identify the pairs of congruent angles and the pairs of congruent sides. Solve each proportion. 2. 3.

3. Congruent ≅ sides and angles are exactly the same. Similar ∼ angles are exactly the same but the sides are proportional Similar figures have a similarity ratio. This is the ratio of the lengths of two corresponding sides. The order in a ratio matters and it must be in the form of a simplified fraction.

4. Figures that are similar (~) have the same shape but not necessarily the same size.

5. A similarity ratio is the ratio of the lengths of the corresponding sides of two similar polygons. The similarity ratio of ∆ABC to ∆DEF is, or. The similarity ratio of ∆DEF to ∆ABC is, or 2.

6. 1.Are the two polygons similar? 2.Find the similarity ratio of ABCD to EFGH. 3.Find the similarity ratio of EFGH to ABCD.

7. 1. What is the similarity ratio of the two similar polygons? Find x and y. 18

8. T RUE OR FALSE If two figures are congruent, they are always similar. If two figures are similar, they are always congruent. The similarity ratio of congruent figures is 1 to 1.

12. T HE FOLLOWING POLYGONS ARE SIMILAR. F IND THE S IMILARITY RATIO OF SMALL TO BIG F IND THE VALUE OF X.

13. Find the length of the model to the nearest tenth of a centimeter.

14. Lesson Quiz: Part I 1. Determine whether the polygons are similar. If so, write the similarity ratio and a similarity statement. 2. The ratio of a model sailboat’s dimensions to the actual boat’s dimensions is. If the length of the model is 10 inches, what is the length of the actual sailboat in feet? 3. Tell whether the following statement is sometimes, always, or never true. Two equilateral triangles are similar.

15. H OMEWORK