1. HONORS GEOMETRY 7.2. Similar Polygons

2. Do Now: The perimeter of a rectangle is 98 feet. The ratio of its length to its width is 5:2. Find the area of the rectangle. A survey of club involvement showed that, of the 36 students surveyed, the ratio of French Club members to Spanish Club members to Drama Club members was 2:3:7. How many of those surveyed participate in Spanish Club? Assume that each student is active in only one club.

3. Homework Questions? Comments? Confusions? Concerns? ASK ASK ASK ASK!

4. Similar Polygons Two polygons are similar if and only if their corresponding angles are congruent and their corresponding sides are proportional. I.E. The same shape but not necessarily the same size.

5. So….. To get triangle congruence we have SSS, SAS, AAS, ASA…. Which of the problem ones will actually yield similar triangles?

6. Realize: Just like order matters with congruent triangles, order matters with similar polygons!

7. Example One:

8. You Try!

9. Scale Factor: The ratio of the lengths of the corresponding sides of two similar polygons. Realize: The scale factor depends on the order of comparison

10. Example Two:

11. Example Three:

12. Example Four: Are the following pairs of polygons similar? If so, write a similarity statement and state the scale factor.

13. You Try! Are the following similar polygons? If so write a similarity statement and state the scale factor

14. Example Five:

15. Example Six:

16. Do Now: Look at your test– where do you go wrong? Do you have questions? Are you confused?

17. You Try!

18. Perimeters of Similar Polygons If two polygons are similar, then their perimeters are proportional to the scale factor between them.

19. Example Seven: Polygon ABCDE~ Polygon PQRST. Find the scale factor of ABCDE to PQRST and the perimeter of each polygon.

20. Example Eight:

21. You Try!

22. Practice Problems Try some on your own/in your table groups As always don’t hesitate to ask questions if you are confused and/or talk to your tablemates– they are your greatest resource!

23. Exit Ticket: Find x and y if triangle ACT is similar to triangle ODG