1. Classifying triangles Written by: James Wiens Newton, Kansas

2. Instructor Notes Subject Area(s): Math Grade level: 7 th grade Lesson Length: 50 minute class period Synopsis: Name triangles by angles and sides. Objective/goals: Students will classify triangles according to types or angles and sides.

3. Standard: ▲ identifies angle and side properties of triangles and quadrilaterals (KS standard 7.3.1.k3) Pre-requisite skills: Vocabulary – Acute, Obtuse, Right, Equilateral, Isosceles, Scalene TurningPoint functions: standard question slides Materials: All instructional points and practice problems are provided within the power point slides. Practice questions are designed to be used with the TurningPoint clickers. Instructor Notes

4. Lesson Outline I.Warm-up: Angle classification II.Setting the Stage: III.Guided practice: Turning Point Questions IV.Independent practice: Paper & pencil V.Closure: Write about triangles

5. Classify this angle: a)Acute b)Right c)Obtuse Classify this angle:

6. a)Acute b)Right c)Obtuse

7. Classify this angle: a)Acute b)Right c)Obtuse

8. Classify by Angles Key concept: Classify the triangle by it’s largest angle. If the largest angle is acute, then the triangle is Acute. If the largest angle is right, then the triangle is Right. If the largest angle is obtuse, then the triangle is Obtuse.

9. Classify by Sides Key concept: Measure the length of each side. If all three sides are the same length, then the triangle is Equilateral. If all two sides are the same length, then the triangle is Isosceles. If all three sides are a different length, then the triangle is Scalene.

10. Setting the Stage A piece of paper is cut diagonally from corner to corner to form a triangle. What kind of triangle is formed based on the length of it’s sides?

11. Answer Scalene

12. Setting the Stage A piece of paper is cut diagonally from corner to corner to form a triangle. What kind of triangle is formed based on the angles formed?

13. Answer Acute

14. Classify this triangle by angles and by sides 1.Acute / Isosceles 2.Obtuse / Isosceles 3.Acute / Scalene 4.Obtuse / Scalene 4 7 7 70 40

15. Classify this triangle by angles and by sides 4 8 90 60 30 9 1.Acute / Isosceles 2.Right / Isosceles 3.Acute / Scalene 4.Right / Scalene

16. Classify this triangle by angles and by sides 1.Acute / Isosceles 2.Obtuse / Isosceles 3.Acute / Scalene 4.Obtuse / Scalene 6 14 18 130 35 15

17. Classify this triangle by angles and by sides 7 7 7 60 1.Acute / Isosceles 2.Right / Isosceles 3.Acute / Equilateral 4.Obtuse / Scalene

18. Independent Practice

20. Answer Key for Independent Practice A.Obtuse / Isosceles B.Acute / Equilateral C.Right / Isosceles D.Acute / Isosceles E.Obtuse / Isosceles F.Acute / Equilateral G.Obtuse / Scalene H.Right / Scalene

21. Closure / Summary Is it possible for an obtuse triangle to also be equilateral? Explain why or why not.

22. References All content of lesson designed and written by James Wiens, 7 th grade math teacher, Newton Kansas.