1. Slide 4-1 Copyright © 2014 Pearson Education, Inc. 2.1 Classifying Triangles

2. Slide 4-2 Definitions A triangle is formed by 3 noncollinear points connected by segments. The noncollinear points are called vertices (singular is vertex). The segments joining the points are called sides. Copyright © 2014 Pearson Education, Inc.

3. Slide 4-3 Definitions Points A, B, and E are vertices. Point A is a vertex. Point B is a vertex. Point E is a vertex. Copyright © 2014 Pearson Education, Inc.

4. Slide 4-4 Example Identifying Parts of a Triangle Given ΔPQR: a. Which angle is opposite segment PQ? b. Which side is opposite angle Q? c. Which side is included between angle P and angle R? d. Which angle is included between segments QR and PR? Copyright © 2014 Pearson Education, Inc.

5. Slide 4-5 Classifying Triangles by Angles and Sides. Copyright © 2014 Pearson Education, Inc. TypeDescriptionExample AcuteAll (3) acute angles Obtuse1 obtuse angle EquiangularAll angles are equal. Right1 right angles

6. Slide 4-6 Classifying Triangles by Angles and Sides. Copyright © 2014 Pearson Education, Inc. TypeDescriptionExample ScaleneNo sides are equal IsoscelesAt least 2 sides are equal EquilateralAll sides are equal

7. Slide 4-7 Definition The Perimeter is the sum of the lengths of a shape’s sides. Example page 69 22, 24 Copyright © 2014 Pearson Education, Inc.

8. Slide 4-8 Example Classifying Triangles Classify each triangle by its angles and sides. Use the most specific name. a. Copyright © 2014 Pearson Education, Inc. AnglesSidesComplete Name RightScalene Right scalene triangle

9. Slide 4-9 Example Classifying Triangles Classify each triangle by its angles and sides. Use the most specific name. b. Copyright © 2014 Pearson Education, Inc. AnglesSidesComplete Name AcuteIsosceles Acute isosceles triangle

10. Slide 4-10 Definitions We call the 3 original angles of a triangle the interior angles of the triangle. The angles that are adjacent to the interior angles are the exterior angles of the triangle. There are two exterior angles associated with each interior angle, but since these two exterior angles are congruent vertical angles, we usually show only one exterior angle with each interior angle. Copyright © 2014 Pearson Education, Inc.