1. Lesson 4-2 Angles of Triangles

2. Ohio Content Standards:

3. Establish the validity of conjectures about geometric objects, their properties and relationships by counter-example, inductive and deductive reasoning, and critiquing arguments made by others.

4. Ohio Content Standards: Make and test conjectures about characteristics and properties (e.g., sides, angles, symmetry) of two- dimensional figures and three- dimensional objects.

5. Theorem 4.1 Angle Sum Theorem

6. The sum of the measures of the angles of a triangle is 180.

7. Find the missing angle measures. 43° 3 2 1 74° 79°

8. Theorem 4.2 Third Angle Theorem

9. If two angles of one triangle are congruent to two angles of a second triangle, then the third angles of the triangles are congruent.

10. Exterior Angle

11. Angle formed by one side of a triangle and the extension of another side.

12. Exterior Angle Angle formed by one side of a triangle and the extension of another side. 1

13. Remote Interior Angles

14. Interior angles of the triangle not adjacent to a given exterior angle.

15. Remote Interior Angles Interior angles of the triangle not adjacent to a given exterior angle. 2 3

16. Theorem 4.3 Exterior Angle Theorem

17. The measure of an exterior angle of a triangle is equal to the sum of the measures of the two remote interior angles.

18. Find the measure of each numbered angle in the figure. 5 4 3 1 2 29° 38° 32° 41° 64°

19. B 20° C A

20. Assignment: Pgs. 189-191 11-35 all, 56-58 evens