1. Warm-up

2. Agenda Chapter 4 Identifying Congruent Triangles 4-1 Classifying Triangles

3. 4-1 Enrichment R S T

4. K L J

5. E F D

6. G I H

7. 4-1 Classifying Triangles Definitions: What is a triangle? A TRIANGLE is a three-sided polygon. So what is a polygon? A POLYGON is a CLOSED figure in a plane that is made up of SEGMENTS that intersect only at their endpoints.

8. 4-1 Classifying Triangles How is a triangle labeled? The SIDES of a triangle are the segments and the VERTICES of the triangle are the endpoints of the segments. In the example above, the side that is OPPOSITE C is. The angle OPPOSITE is  A.

9. 4-1 Classifying Triangles An ACUTE triangle has THREE acute angles. The dotted lines represent potential boundaries for the acute triangle. If it were to touch one of these lines it would change its name. What would it be?

10. 4-1 Classifying Triangles The dotted lines represent potential boundaries for the obtuse triangle. If it were to touch one of these lines it would change its name. What would it be? An OBTUSE triangle has ONE obtuse angle.

11. 4-1 Classifying Triangles A RIGHT triangle has ONE right angle. The animation shows a number of possible shapes which a right triangle could have.

12. 4-1 Classifying Triangles

14. SCALENE Triangle - NO sides are congruent. (3 different sides)

15. 4-1 Classifying Triangles ISOSCELES Triangle - AT LEAST TWO sides are congruent.

16. 4-1 Classifying Triangles EQUILATERAL TRIANGLE - ALL the sides are congruent.

17. 4-1 Classifying Triangles

21. Do the following triangles exist? a right isosceles triangle a right equilateral triangle a right scalene triangle an acute scalene triangle an acute isosceles triangle an obtuse scalene triangle an obtuse isosceles triangle an obtuse equilateral triangle an acute equilateral triangle......

22. Answers Ahead

23. 4-1 Study Guide

24. Homework 4-1 Study Guide and Practice