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LESSON NO. 3
DATE: NOVEMBER 15 ,2007
COMPETENCIES D1. 2. Base angles and diagonals of a trapezoid.
I. Objectives
1. To show that in isosceles trapezoid the legs are congruent, the base angles are
congruent and the diagonals are congruent.
2. To show that the median of a trapezoid is parallel to the bases and its length is
equal to one half the sum of their lengths.
II. Subject- Matter
Reference
Resources
: The trapezoid and its Properties
: Geometry textbook by C.M de Leon pages 122-123
: protractor, ruler, pencil, internet, printer
A. Introductory activity
a. Drill. : what are the different kinds of quadrilaterals?
b. Review
:
What is a trapezoid?
B. Development of the lesson
1. Main Activity ( On-line activity )
Pre- activity
1. Assign three (3) students in each computer.
2. Ask the students to open the internet explorer.
3. Allow the students to work the activity for 15 minutes found in chapter 4, lesson 3 student
activity of the website www.nti6.wikispaces.com
4. Select group to present their answers on the guide questions using a PowerPoint
presentation.
5. Tell the other groups to submit a printed copy of their outputs.
STUDENT ACTIVITY 1
1. On the computer, double click Microsoft Word icon on the desktop.
2. Draw an isosceles trapezoid ABCD, where BA and CD are the legs; AC and BD are
diagonals. Then print.
2.1 Using a protractor, measure A and D. what can you say about their measures?
2.2. With a ruler, measure the diagonals. What did you find out?
STUDENT ACTIVITY 2
3. Cut the drawing and Fold the cut –out such that the parallel sides will coincide with each
other.
- What does the crease of the fold represent?
- Mark the endpoints of the median E and F as shown below:
A
E
D
B
F
C
-
Measure AE and ED ; BF and FC . What do you observe?
What relationship exists between AB and EF ? EF and DC ?
Add the measures of AB and DC and get one half of their sum.
Measure EF . What do you observe?
Take note all your answers on the questions and present it using a PowerPoint.
3. Post Activity Discussion
Output presentation by selected group.
C. Fixing skills ( in Powerpoint)
P
1. PART is an isosceles trapezoid.
- Name the bases of the figure.
- Which Two segments are parallel? Why?
- Which two segments are congruent? Why?
- How do you call AT and PR ?
T
A
R
2. Solve for x.
16
x
10
D. Generalization
What are the parts of the trapezoid?
What can be said about the legs of an isosceles trapezoid? Its base angles? its diagonals?
What can be said about the median of a trapezoid? The length of the median?
How do we determine the median of a trapezoid?
IV.
Evaluation ( ON LINE QUIZ)
1. A trapezoid has congruent sides. We call the congruent sides the _________ and the
parallel sides the ___________. The base angles of an isosceles trapezoid are _________.
2. ABCD is a trapezoid with segment EF as a median.
- if AB = 7 and DC = 11. what is the length of EF ?
- If EF = 11.5 and AB = 7. what is the measure of DC ?
V.
Agreement
Answer Test Yourself nos. 5 – 10 , page 123. Geometry Textbook