1. Types of Triangles
Geometry 3.6

2. Classification by Sides with Flow Charts & Venn Diagrams
polygons
Polygon
triangles
Triangle
scalene
isosceles
Scalene
Isosceles
equilateral
Equilateral
Lesson 3-1: Triangle Fundamentals

3. Classification by Angles with Flow Charts & Venn Diagrams
polygons
Polygon
triangles
Triangle
right
acute
equiangular
Right
Obtuse
Acute
obtuse
Equiangular
Lesson 3-1: Triangle Fundamentals

4. Types of Triangles by Lengths of Sides.
Definition: SCALENE a triangle in which no sides are congruent.

5. Types of Triangles by Lengths of Sides.
Vertex Angle
Definition: ISOSCELES a triangle in which at least 2 sides are congruent.
Base Angles

6. Types of Triangles by Lengths of Sides.
Definition: EQUILATERAL a triangle in which all sides are congruent.
**EQUILATERAL applies to any figure in which all sides are congruent**

7. Types of Triangles by Lengths of Sides.
An Equilateral Rectangle is a
SQUARE.

8. Types of Triangles by Size of Angles.
Definition: ACUTE Triangle a triangle in which all angles are acute.

9. Types of Triangles by Size of Angles.
Definition: RIGHT Triangle a triangle in which one of the angles is a right angle.

10. Types of Triangles by Size of Angles.
Definition: OBTUSE Triangle a triangle in which one of the angles is an obtuse angle.

11. Types of Triangles by Size of Angles.
EQUIANGULAR: a triangle in which all angles are congruent.
**EQUIANGULAR applies to any figure in which all angles are congruent**

12. Example: Given: m<CBD = 70 Prove: Triangle ABC is obtuse
Proof: m<CBD = 70º and <ABD is a straight angle, so m<ABC = 110º. Since ΔABC contains an obtuse angle, it is an obtuse triangle.

13. Homework Help…#15
There are three possible diagrams that satisfy this description.