1. Isosceles Triangles Geometry Ms. Reed Unit 4, Day 2

2. Parts of an Isosceles Triangle Legs Base

3. Parts of an Isosceles Triangle Vertex Angle Base Angles

4. With your Isosceles Triangle: Measure all three sides and angles With a partner, discuss your results. What did you notice?

5. Three Triangle Postulates 4-1: If two sides of a triangle are congruent, then the angles opposite those sides are also congruent.

6. What it looks like: http://www.usna.edu/Users/cs/lmcdowel/courses/ic210/F07/labs/IC210_Lab_3_IsoscelesTriangle.gif

7. How to use it: http://education.yahoo.com/homework_help/math_help/solutionimages/minigeogt/4/1/1/minigeogt_4_1_1_19_30/f-226-31-ex-1.gif Find x.

8. Three Triangle Postulates 4-1: If two sides of a triangle are congruent, then the angles opposite those sides are also congruent. 4-2: The bisector of the vertex angle of an isosceles triangle is the perpendicular bisector of the base.

9. What it looks like: CD is the bisector of  ACB. Make the appropriate markings on the triangle using Theorem 4-2.

10. How to use it: Find the perimeter and area of the triangle.

11. Three Triangle Postulates 4-1: If two sides of a triangle are congruent, then the angles opposite those sides are also congruent. 4-2: The bisector of the vertex angle of an isosceles triangle is the perpendicular bisector of the base. 4-3: If two angles of a triangle are congruent, then the sides opposite the angles are congruent.

12. What is looks like:

13. How to use it:  A   B, BC = 5. Find AC. A B C 5

14. Practice Find the values of x and y.

15. Homework Work Packet: Isosceles Triangles