1. Classify These Triangles by Sides and Angles

2. Chapter 4 Congruent Triangles Section 4.1: Triangle Sum Properties Todays Objective: Determine if a right triangle can be an obtuse triangle and explain why or why not.

3. Triangle Classifications By Sides: Equilateral Triangle – All sides have the same length By Angles: Equiangular Triangle – All internal angles have the same measure

4. Triangle Classifications What do we call a polygon that is both equilateral and equiangular? What is the sum of the measures of the interior angles of any triangle? Regular Polygon Theorem 4.1: Triangle Sum Theorem The sum of the measures of the interior angles of any triangle is 180°

5. Triangle Classifications By Sides: Isosceles Triangle – Two sides have the same length By Angles: Acute Triangle – All internal angles are acute.

6. Triangle Classifications By Sides: Scalene Triangle – All sides have different lengths By Angles: Obtuse Triangle – One internal angle is obtuse

7. Triangle Classifications By Sides: Scalene or Isosceles Triangle – At least one side (the hypotenuse) must be longer than the other two. By Angles: Right Triangle – One internal angle is a Right Angle (measures 90°)

8. Angle Measures a c b d Angle d and Angle c are a ___________

9. Theorem 4.2 Exterior Angle Theorem The measure of the exterior angle of a triangle is equal to the sum of the measures of the two nonadjacent interior angles

10. Right Triangles Can a right triangle ever be an obtuse triangle? B A The Acute angles of a Right Triangle must be Complementary.

11. Homework Section 4.1 p.221 # 1 - 7, 15 – 17, 21 – 26