1. Similar Triangles Section 7.4
Curriculum Outcome: Demonstrate an Understanding of Similar Polygons

2. Properties of Similar TrianglesD
To identify that ∆ABC and ∆DEF are similar, we only need to know that:
<A=<D and <B=<E and <C=<F; or
AB~ DE and BC~ EF and AC~ DF A B C E F

3. Properties of Similar TrianglesD
So because of this ∆ABC and ∆DEF are similar. A B C E F

4. Properties of Similar Triangles
Let’s try this with triangles off a grid…Similar or not? K
30o J B
90o
30o C
60o
60o
90o A L

5. Properties of Similar Triangles
Regardless of orientation, the corresponding angles are equal, so ∆ABC~∆JKL. K
30o J B
90o
30o C
60o
60o
90o A L

6. Properties of Similar TrianglesJ
What about these two triangles? O × X Y O × G P

7. Properties of Similar TrianglesJ J 2 2 O × X Y 5
What if we wanted to determine side GP?
How could we use our knowledge of similar triangles? 4 O × G P

8. Properties of Similar TrianglesJ J 2 2 O × X Y 5 4
Now we can use corresponding sides to determine our missing side: GP. O × G P

9. Properties of Similar TrianglesJ J 2 2 6 O × X Y 5 4 O × G P

10. Properties of Similar TrianglesJ J 2 6 O × X Y 5 O × G P

11. Properties of Similar Triangles6 4
2.5
7.5 5 5 4 6 6
!!!APPLAUSE!!!

12. Properties of Similar TrianglesU 6 4 S
7.5 Q 5 T
So now what?
What are the corresponding sides?
What are the corresponding angles? 6 R

13. Properties of Similar TrianglesU 6 4 S
7.5 Q 5 T 6 R

14. Properties of Similar TrianglesU 6 4 S
7.5 Q 5 T 6 R

15. Properties of Similar TrianglesU 6 4 S
7.5 Q 5 T 6 R

16. Properties of Similar TrianglesU 6 4 S
7.5 Q 5 T 6 R

17. Properties of Similar TrianglesU 6 4 S
7.5 Q 5 T 6 R

18. Assignment Time Pg
#3,4,5,6, 7, 8, 9,12,13,15