1. Did you observe any triangles this weekend?
Problem of the Day

2. A triangle that saves my kids’ lives…

3. A triangle that saves my life…

4. A triangle I use every day…

5. A triangle I like to eat…

6. We also see triangles in…
FLAGS
FASHION
We also see triangles in…
NATURE

7. Section 4-1 Classifying Triangles

8. Then Now Objectives You measured and classified angles.
Identify and classify triangles by angle measures.
Identify and classify triangles by side measures.

9. Common Core State Standards
Content Standards
G.CO.12 – Make formal geometric constructions with a variety of tools and methods.
Mathematical Practices
2) Reason abstractly and quantitatively.
6) Attend to precision.
Common Core State Standards

10. Classifications of Triangles by Angles

11. Classifications of Triangles by Sides

12. What is the sum of the interior angles of a triangle?
Do you remember?
180°

13. Classifying Triangles
In your groups, sort the triangles according to both the side lengths and angle measures. Some triangles fit into more than one category. Make sure you choose the most specific category. Keep in mind, any information given outweighs how a figure looks. The number of squares in each category shows how many items are in that category.
Classifying Triangles

14. Find the length of each side of equilateral ∆EDF.
Example 5

15. Find the length of each side of isosceles ∆RST with RS = TS.
Example 5

16. △FGH is an equilateral triangle with FG = x + 5, GH = 3x – 9, and FH = 2x – 2. Find x and the perimeter of the triangle.
Example 5

17. △LMN is an isosceles triangle, with LM = LN, LM = 3x – 2, LN =2x + 1, and MN = 5x – 2. Find x and the perimeter of the triangle.
Example 5

18. p.240 #12, 13, 21 – 29, 36, 37, 49, 50, 82 – 85
Homework