1. September 6, 2013 1) Sit. 2) Materials out. 3) Backpacks away
September 6, ) Sit. 2) Materials out. 3) Backpacks away. 4) Do Now SILENTLY.
Learning Goal:
IWBAT to determine whether given side lengths form triangles and solve for unknown angles in triangles.
Homework:
HW 3.2: Triangle Inequality Worksheet
HW 3.3A: Triangle Sum Theorem Worksheet
Do Now:
Find the measure of the unknown angles shown below.
Students take out Do Now sheets.
Remind students to take out homework to be checked, copy new homework assignment in their agenda, and copy down learning goal BEFORE beginning the Do Now problem.
Take roll first, then go around and check homework as students are working.

2. Agenda: Do Now (10 min) Explore Triangle Inequalities (15 min)
Triangle Inequality Theorem (30 min)
Constructing Triangles (15 min)
Triangle Proofs (15 min)
Whiteboard Activity (30 min)
Closure (5 min)

3. Triangle Experiment Each pair will receive straws of different lengths
Select three straws with the given lengths and test whether the straws form a triangle.
Check off the “Yes” or “No” box.

4. Triangle Experiment
Try to find some common characteristics for the sets of side lengths that DO form a triangle.
Try to find some common characteristics for the sets of side lengths that DO NOT form a triangle.
Come up with a rule that can predict whether three side lengths will form a triangle.

5. Triangle Inequality Theorem

6. Triangle Inequality Theorem

7. Triangle Inequality Theorem

8. Triangle Inequality Theorem

9. Construct a Triangle
Construct a triangle that has side lengths 3 cm, 4 cm, and 5 cm.
Teacher will demonstrate to the class how to construct the triangle.
You can also follow the steps presented in the handout.
Construct a triangle with the following lengths. Some sets of given lengths will form triangles while others will not.
1 cm, 1cm, 2 cm
4 cm, 5cm, 2 cm

10. Review Triangle Theorems

11. Triangle Proofs Given m<ABC = 30 m<BCA = 20 Prove m<DAE = 130

12. Triangle Algebra Activity
Students break up into groups of 3 or 4. Groups have been predetermined. Each group receives a whiteboard, marker, and eraser.
Teacher will present practice exercises about triangles on the board.
Your teams have 2 minutes to solve the problem and write the answer on the whiteboard with its justification.
The correct answer receives 1 point. The correct justification receives an additional point.
Explain the activity to the class. Activity is open notes/ open book.

13. Geometry Period 2 Teams Yellow Team Oscar E. Jazmin A. Nancy L.
Red Team
George O.
Mayra R.
Charles L.
Ashley T.
Green Team
Ben M.
Kathy M.
Christian V.
Brisya C.
Purple Team
Linda
Jovanny H.
Adolfo G.
Justlene S.
Yellow Team
Oscar E.
Jazmin A.
Nancy L.
Orange Team
Ben L.
Susana A.
Abel P.
Blue Team
Jose L.
Carina A.
Jackie D.
Miguel B.

14. Geometry Period 4 Teams Green Team Purple Team James L. Lee Ann Q.
Red Team
Dennise P.
Amanda V.
Seth F.
Javier G.
Green Team
Veronica S.
Oscar S.
Lorena G.
Alfonso M.
Purple Team
James L.
Lee Ann Q.
Mirna A.
Thea Q.
Yellow Team
Jesus R.
Ariana P.
Leslie V.
Erick M.
Orange Team
Christina G.
Derek A.
Yuleni V.
Blue Team
Angie Z.
Miranda D.
Arthur D.
Sydney G.

15. Geometry Period 6 Teams Green Team Christina R. Geovanni B. Oscar G.
Red Team
Freddy A.
Anthony S.
Hannya O.
Ashley L.
Green Team
Christina R.
Geovanni B.
Oscar G.
Sabrina L.
Purple Team
Alexis A.
Deborah H.
Sabrina O.
Cristian B.
Yellow Team
Paulina C.
Martin R.
Melissa R.
Jonathan T.
Orange Team
Steven P.
Wendy G.
Abel P.
Leslie H.
Blue Team
Jose S.
Jailene L.
Abigail G.
Andy H.

16. Exercise #1 Find the measure of the unknown angle shown below.
45 degrees

17. Exercise #2 Find the measure of the unknown angle shown below.
30 degrees

18. Exercise #3 Find the measure of the unknown angle shown below.
85 degrees

19. Exercise #4 Find the measure of the unknown angle shown below.
21 degrees

20. Exercise #5 Find the measure of the unknown angle shown below.
135 degrees

21. Exercise #6 Find the measure of the unknown angle shown below.
145 degrees

22. Exercise #7 Find the measure of the unknown angle shown below.
64 degrees

23. Exercise #8 Find the measure of the unknown angle shown below.
31 degrees

24. Exercise #9 Find the measure of the unknown angle shown below.
137 degrees

25. Exercise #10 Find the measure of the unknown angle shown below.
109 degrees

26. Triangle Theorem Masters
Period 1
Period 2
Miguel B.
Jose L.
Jackie D.
Carina
Period 3
Period 5
Period 6
Oscar G.
Christina R.
Sabrina L.
Geo B.
Period 4
Jesus R.
Ariana P.
Leslie V.
Eric M.

27. Closure
Take a moment to response to the following prompts on a flashcard.
Why do the angles of any triangle add up to 180 degrees?
The angles of any triangle add up to 180 degrees because ___________________________ .
What conditions must three sides satisfy in order for the sides to form a triangle?
In order for sides to form a triangle, _____________________ .
109 degrees