1. Solve the following for x:
DO NOW 12/1:
Solve the following for x: 1. 2. 3.
Triangle Similarity
Agenda
Embedded Assessment Review/Note Check
Intro to Similarity
Definition of Scale Factor
Proportions Practice
Debrief

2. Similarity and Scale
“Similarity” means two figures that have the same relative shape but are different sizes. We sometimes say that similar figures have been “scaled” up or down.
What are some things we have done in class or in real life that use “scale”?
Many tablets and phones have the ability to “scale” images on the screen using “pinching” gestures.
How did the phone designers write this code?
What steps does the program have to take to keep the image recognizable?
**MUST BE IN NOTES!**

3. Scale Factor
**MUST BE IN NOTES!**
The “scale factor” (r) is the ratio of any length in a scale drawing relative to the length of the corresponding length in the original.
If r > 1, than the scale figure is larger
If 0 < r < 1, than the scale figure is smaller
Ex. What would “r” be between the SMART Board model calculator and the calculators on your desks?

4. Proportions Review
**MUST BE IN NOTES!**
A proportion describes two different ratios or fractions that are equivalent or equal.
To solve, just like any fraction we would get rid of the denominators by multiplying on both sides and then compare the numerators. The easiest method to remember to do this is called “cross-multiply”
What are some examples of things that increase proportionally in real life?
20x = 36
x = 36/20
x = 1.8

5. Creating Scale Triangles Jigsaw
In Groups – Come up with a method to complete Example 1. **Everyone prepared to explain and show your groups work!**
10 min – develop method in groups
9 min (3 min each) – one person stays to explain, others switch
--- DISCUSSION BREAK----
In Groups – Come up with a method to complete Example 2. **Everyone prepared to explain and show your groups work!**

6. Debrief What was the best method? Why?
What makes a good scale drawing?
How are scale drawings related to similarity?

7. Triangle Similarity: Construction and Scale Factor
DO NOW 12.2:
Are △ABC and △DEF similar? Explain how you know.
Triangle Similarity: Construction and Scale Factor
Agenda
Similarity Statements and Proportions
Jigsaw (ex. 1 and ex. 2)
Debrief
Problem Set Exercises

8. Similarity Statements and Proportions
**MUST BE IN NOTES!**
Similarity statements are written the same way as congruence statements; in the order that they are similar.
If triangles are similar, you can write a proportion using any two sets of corresponding sides.
“similar”
△ABC ~ △DFE

9. Similarity Examples

10. Example 1

11. Creating Scale Triangles Jigsaw
In Groups – Come up with a method to complete Example 1. **Everyone prepared to explain and show your groups work!**
8 min – develop method in groups
4 min (2 min each) – one person stays to explain, others switch
--- DISCUSSION BREAK----
What method did we use to create similar triangles?
What is true about the sides of similar triangles?
What do we notice about the angles? What has to be true of the angles in similar triangles?
In Groups – Come up with a method to complete Example 2. **Everyone prepared to explain and show your groups work!**

12. Example 2

13. Debrief
What are the parts of a triangle needed to create a good scale drawing of a figure?
What is the term for the constant rate by which all lengths are increased in a scale drawing?
If in Example 1 we took all the same steps but our triangle was drawn upside down, would the drawing still have been a scale drawing?

14. Triangle Similarity: AA Congruence
DO NOW 12/3:
Triangle Similarity: AA Congruence
Agenda
Proportions Practice
Lesson 1 Review
AA Similarity
Exit Ticket/Debrief

15. Practice With Proportions

16. Practice With Proportions, cont.

17. Lesson 1 Review

18. Lesson 1 Review, cont.

19. Exit Ticket

20. Triangle Similarity Shortcuts Quiz
DO NOW 12/4:
Are the two triangles similar?
Explain why or why not.
Triangle Similarity Shortcuts Quiz
Agenda
Quiz/Note Check
Embedded Assessment 2 (Review)
Embedded Assessment 3 (when Quiz is finished)
Lesson 15 – AA Similarity
Debrief

21. Embedded Assessment 2 (Review)

22. Debrief What has to be true of similar triangles?
What are some differences between congruence and similarity?
How will we need to change our triangle congruence shortcuts (ASA, etc.) for similarity?

23. Triangle Similarity: Angles on Parallel Lines
DO NOW 12/5:
Triangle Similarity: Angles on Parallel Lines
Agenda
Quiz Review
Embedded Assessment: Screen Resolution
AA Similarity Packet
Debrief