1. Circle the ways that Triangles can be congruent: SSS SAS SSA AAA AAS

2. Proving Triangles Similar Geometry Unit 11, Day 6 Ms. Reed

3. Similar Triangles Similar Triangles have congruent angles a similarity ratio between the corresponding sides. The sign for similarity is ~

4. In groups of 2: We will be discovering ways to prove triangles similar. You will need: calculator ruler protractor scrap paper

5. Is AA a way to prove triangles similar? In your groups, each draw a large triangle with a 50° and a 60° angle Measure the sides of the triangle to the nearest 1/16 Find the ratio of the corresponding sides ARE THE TRIANGLES SIMILAR?

6. Is SAS a way to prove triangles similar? In your groups, each person draw an angle that is 90° Using a similarity ratio of ½, proportionally draw the 2 sides that include the angle. ARE THE TRIANGLES SIMILAR?

7. Is SSS a way to prove triangles similar? With a partner, pick the lengths of both triangles with a similarity ratio of ½. **Use a special right triangle to keep in easier** Draw each of the triangles. **Start with a 90° angle. Measure the angles of the triangles. ARE THE TRIANGLES SIMILAR?

8. Triangle Similarity We can use AA, SAS, and SSS to prove triangles congruent.

9. Example 1 Are these triangles similar? Why? 45 

10. Example 2 Are these triangles similar? Why? 9 12 66 88

11. Example 3 Are these triangles similar? Why? 9 7 14 18

12. Solving for a missing side: How are we going to find x?! Set up a proportion! 5 4 12 x

13. Solving for a missing side: 12 = x 4 5 5 4 12 x What side of one triangle corresponds with what side of the other? x = 15

14. Example 4 Find the value of x 6 x 98

15. Homework Work Packet: Triangle Similarity