Download Geometry Fall 2011 Lesson 17 (S.A.S. Postulate)

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Lesson Plan #36
Date: Wednesday November 28th, 2012
Class: Geometry
Topic: Exterior angle of a triangle
Aim: What is the relationship between the exterior angle of a triangle and the 2 remote interior angles of the triangle?
Objectives:
1) Students will know the relationship between
an exterior angle of a triangle and the 2
remote interior angles of the triangle.
HW #36:
Do Now:
1) What is it called when two simple statements
are joined with the word and?
A) Disjunction
B) negation
C) Biconditional
D) conjunction
2)
PROCEDURE:
Write the Aim and Do Now
Get students working!
Take attendance
Give Back HW
Collect HW
Go over the Do Now
Assignment #1: Complete the proof below
Given: ∆𝐴𝐵𝐶 with exterior < 𝐶𝐵𝐷 at vertex 𝐵
Two non-adjacent interior angles < 𝐴 and < 𝐶
Prove: 6.𝑚 < 𝐶𝐵𝐷 = 𝑚 < 𝐴 + 𝑚 < 𝐶
Statements
1. ∆𝐴𝐵𝐶 with exterior < 𝐶𝐵𝐷 at vertex 𝐵
2. < 𝐶𝐵𝐷 and < 𝐶𝐵𝐴 form a linear pair
3. 𝑚 < 𝐶𝐵𝐷 + 𝑚 < 𝐶𝐵𝐴 = 180
4. 𝑚 < 𝐴 + 𝑚 < 𝐶𝐵𝐴 + 𝑚 < 𝐶 = 180
5.𝑚 < 𝐶𝐵𝐷 + 𝑚 < 𝐶𝐵𝐴 = 𝑚 < 𝐴 + 𝑚 < 𝐶𝐵𝐴 + 𝑚 < 𝐶
6.𝑚 < 𝐶𝐵𝐷 = 𝑚 < 𝐴 + 𝑚 < 𝐶
Reasons
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2. A linear pair of angles are two angles whose sum is a straight angle.
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Theorem: The measure of an exterior angle of a triangle is equal to the sum of the measures of the
two non-adjacent interior angles.
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Online Interactive Activity : Let’s go http://www.mathopenref.com/triangleextangle.html and see the relationship
between an exterior angle of a triangle and the two remote interior angles.
Assignment #1:
Find 𝒎 < 𝐿𝐾𝑁
Assignment #2:
If the measure of the exterior angle = (3x - 10) degrees and the measure of the two remote
interiors angles are 25 degrees and
(x + 15) degrees, find x.
Assignment #4: Find the values of 𝑥 and 𝑦 in the diagram at right.
Assignment #5:
Assignment #6:
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