1. Entry Task

2. 7-2 Similar Polygons

3. Read the first page of the handout about Similar Polygons. Then answer the following questions and discuss with a partner.  What does it mean if two figures are similar?  What does it mean if two figures are congruent?  Are all rectangles similar? What about circles, squares, and triangles?

4. Investigation 1  Do the investigation on the back page of the handout.  You will need patty paper and a ruler.  Answer the questions in steps 1-3 in your notes.  How do the corresponding angles compare?  How do the ratios of the corresponding sides compare?

5. Definition of similar polygons  Two polygons are similar if and only if the corresponding angles are congruent and the corresponding sides are proportional.  So what does all that mean?

6.  When three or more ratios are equal, you can write an extended proportion.  A scale factor is a ratio of corresponding linear measurements of two similar figures.  So the scale factor of ABCD to GHIJ is.

7.  Are the triangles similar?  First identify pairs of congruent angles.  Now compare the ratios of corresponding sides. 12 C AB 8 16 F E D 20 15 10

8. A BC D E F G H Identify pairs of congruent angles. Compare the ratios of corresponding sides. Corresponding sides are not proportional, so the polygons are not similar. 6 12 24 16 6 14 6 Are the following polygons similar?

9.  CORN~PEAS C O R N P E A S 8 cm 9 cm 4 cm 72˚ Find the values of x and y. x y Example

10. Another example These pentagons are similar. Find the values for x, y, and z. 5 cm 4 cm 4.7 cm 7 cm 7.5 cm x y z

11. Time to practice…  In your textbook do the Lesson Check exercises 1-8 on page 444. These should be done in your notes.

12. Homework! Page 444 (9-20 all, 22-29 all, 32, 34, 38)