Download LESSON 6.Angles of a Parallelogram

LESSON NO. 6
DATE: OCTOBER ,2007
COMPETENCIES D1. 3 Angles of a Parallelogram
I. Objectives
1 To derive that the following property of a parallelogram and apply theses in
problem solving:
a. opposite angles are congruent.
b. Non- opposite angles are supplementary
II. Subject- Matter
Reference
: Angles of a Parallelogram
: Geometry textbook by C.M de Leon pages 123-124
http://regentsprep.org/Regents/math/quad/JavaParallel.htm
www.samgierlessons.wikispaces.com
Resources
: ruler, pencil, internet, protractor, computer, TV
A. Introductory activity
a. Drill. : What is an angle? What are supplementary angles?
b. Review
:
What is a parallelogram?
B. Development of the lesson
1 .( Off-line activity )
Title: REVISITING PARALLEL LINES
Activity A
1. Divide the class into four (4) groups.
2. Ask a volunteer to draw parallelogram BANK on the board with its sides extended.
3. Label the angles formed as shown below.
5
6
7 8
B
2
K
1
4
A
3
N
4. Ask each group to answer the following questions orally.
a. Name two pairs of opposite angles of parallelogram BANK.
b. Name four pairs of consecutive angles
c. How are 1 and 6 related?
d. How are 7 and 4 related?
e. How are 6 and 4 related?
f. How are 7 and 1 related?
g. How are 7 and 3 related?
h. How are 6 and 2 related?
5. Relate the activity with the lesson
Activity B. ANGLES OF A PARALLELOGRAM
1. Show a PowerPoint presentation of the figure shown above.
2. Ask the students to share their observations on the figure: Guide them by asking the
following questions:
a. If m1 =100, what is the measure of the other numbered angle?
b. Describe the relation obtained between the following angles
- 1 and 3 and 2 and 4
- 2 and 1, 3 and 4, 4 and 1, 3 and 2
c.
d.
e.
f.
What do you call 1 and 3? 2 and 4?
What is your observation about the opposite angles?
What do you call 1 and 2? 2 and 3?1 and 4? 3 and 4?
What can be concluded about the consecutive angles?
3. Post Activity Discussion
Illustrate the concept further by giving the following exercises: ( In Powerpoint)
L
O
E
V
1. LOVE is a parallelogram.
a. Name the pairs of opposite angles and consecutive angles.
b. Name the pairs of parallel sides.
c. If mL = 95, find the measure of the other angles.
d. If mL = 3x – 20 and mL = x + 40. Find the measure of each angle.
D. Generalization
What is true about the opposite angles of a parallelogram?
What is true about the non-opposite angles of a parallelogram?
IV.
Evaluation ( ON LINE QUIZ)
C
U
40º
E
T
CUTE is a parallelogram.
1. If C = 85º. Find the measure of the other angle?
2. If mT = 2x – 1 and mC = 3x + 5. Find the measure of each angle
V.
Agreement
Answer Test yourself nos. 1- 15, page 127-128
Geometry Textbook
Reference: CHAPTER 4, www.samgierlessons.wikispaces.com