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

1
Lesson Plan #33
Date: Thursday December 3rd, 2015
Class: Geometry
Topic: Sum of the measures of the angles of a triangle
Aim: How do we solve problems involving the sum of the angles of a triangle?
Objectives:
1) Students will be able to solve problems
involving the sum of the angles of a triangle.
HW #33:Finish all questions at the end of the lesson plan.
Do Now:
1) If two lines cut by a transversal are parallel
what is true of the corresponding angles?
A) The angles are supplementary
B) The angles are complementary
C) The angles are right angles
D) The angles are congruent
2)
3) Find the measure of each angle
PROCEDURE:
Write the Aim and Do Now
Get students working!
Take attendance
Give Back HW
Collect HW
Go over the Do Now
Assignment #1:
Hands on Activity:
⃡ .
In the triangle above, using a straight edge, draw a line ⃡𝐷𝐸 through B parallel to 𝐴𝐶
Label angle DBA as < 1 and label angle EBC as < 2.
Question:
1) What is the sum of m<1 + m<ABC + m<2?
2) What do we know about < 𝐴and < 1?
3) What do we know about < 𝐶and < 2?
4) Based on your answers to questions 2 and 3, how can we
rewrite the expression in question 1?
Theorem: The sum of the degree measures of the
angles of a triangle is 180.
2
http://www.geogebra.org/en/upload/files/english/Barbara_Perez/Triangle_Angle_Sum.html
Assignment #2: What is the measure of the third angle in each
triangle at right? Why
Corollary: If two angles of one triangle are
congruent, respectively, to two angles of another
triangle, then the third angles are congruent.
Assignment #3: Classify the triangle at right.
What is the measure of each angle in the triangle at right? Why?
Corollary: Each angle of an equilateral triangle measures 60o.
Assignment#4: How would you classify the triangle at right?
What do we know about the sum of the acute angles in this right triangle?
Corollary: The acute angles of a right triangle are complementary
What is the measure of each acute angle in this isosceles right triangle?
Corollary: Each acute angle of an isosceles right triangle measures 45 o.
Assignment #5: Classify the figure at right
We are looking to find the sum of the angles of a quadrilateral. To help us with this, draw a
diagonal in the quadrilateral. What have we created?
What is the sum of the angles of a quadrilateral?
Corollary: The sum of the degree measures of the angles of a
quadrilateral is 360.
Assignment #6:
Assignment #7:
3
Assignment #8:
Assignment #9:
Assignment #10:
Assignment #11:
Assignment #12:
Assignment #13:
4
Sample Test Questions:
1)
3)
5)
7)
8)
2)
4)
6)
9)
5
10)
11)
11)
12)
13)
14)
15)