1. Triangles Geometry Mr. Zampetti Unit 3, Day 1

2. Today’s Objectives To learn new strategies that will help find the measures of angles in a triangle To learn how to classify triangles

3. Triangle Activity 1.Draw and cut out a large triangle. 2.Number all three angles of the triangle 3.Tear of the angles 4.Place the 3 angles adjacent to each other to form one angle Compare your results with a partner. Make a conjecture about the sum of the angles of a triangle.

4. Theorem 2-1 Triangle Angle-Sum Theorem The sum of the measures of the angles of a triangle is 180 .

5. Video: Sum of the Angles of a Triangle

6. Find the measure of the missing angle http://www.mathsisfun.com/geometry/images/triangle-missing-angle.gif http://maths.fallibroome.cheshire.sch.uk/triangle.jpg http://www.gizapyramid.com/basic_triangle_w-angles.gif x x

7. Practice Find all Variables:

8. Practice Find all Variables:

9. Practice Find all variables

10. Definition Exterior Angle: an angle formed by the side of a polygon and an extension of a side. http://www.freemathhelp.com/images/lessons/exterior1.gif

11. Definition Remote Interior Angle: the two nonadjacent interior angles to an exterior angle. http://www.freemathhelp.com/images/lessons/exterior1.gif

12. Activity! Draw a triangle with an Exterior Angle like this: Measure all of the angles. With a partner, make a conjecture about the exterior angle and the remote interior angles.

13. Theorem 2-2 Exterior Angle Theorem The measure of each exterior angle of a triangle equals the sum of the measures of its two remote interior angles.

14. Find the measure of the missing angle http://www.kwiznet.com/px/homes/i/grade8/math/Grade_VIII_Triangles_And_Polygons_PB2_QuestionNo.5.gif

15. Find the measure of the missing angle http://www.freemathhelp.com/images/lessons/exterior2.gif

16. Definition Corollary: a statement that follows directly from a theorem.

17. Corollary to Theorem 2-2 The measure of an exterior angle of a triangle is greater than the measure of either of its remote interior angles.

18. Types of Triangles (by sides) Equilateral Isosceles Scalene

19. Equilateral Triangles Definition: –A triangle with three congruent sides. Example:

20. Isosceles Triangles Definition: –A triangle with two congruent sides. Example:

21. Scalene Triangles Definition: –A triangle with no congruent sides. Example:

22. Types of Triangles (by angle) Equiangular Acute Right Obtuse

23. Equiangular Triangles Definition: –A triangle with three congruent angles. Example:

24. Acute Triangles Definition: –A triangle whose angles are all acute. Example:

25. Right Triangles Definition: –A triangle with one right angle. Example:

26. Obtuse Triangles Definition: –A triangle with one obtuse angle. Example:

27. Triangle Video Triangle video!!

28. Homework Work Packet: Triangles