1. Name of the teacher : Neethu Krishnan
Subject : Mathematics
Unit : circle
Subunit : circle -Theorem
Name of the school : Mount Tabor Training college
Pathanapuram
Standard : 9 .c
Strength : 44/47
Date :10/8/2015
Time :30 min
CURRICULAR STATEMENT: To understand about the problem of circle and its importance in
mathematics through observation, organization of charts and by analyzing prepared notes of the pupil.
CONTENT ANALYSIS
New term : congruent triangle.
Fact : If two angles of two triangle are equal, then the third angle also will be equal.
Concept : Concept of problem on circle.
Process : process of understanding the problem of circle.
2. LEARNING OUTCOMES
The pupil will be able to :-
(1) recall the term bisector
(2) Recognize right angle triangle.
(3) Concept of bisector of two equal chords.
(4) explain chord of equal length.
(5) Suggest a different method to prove chords of equal lengths are at equal distance from the
Center.
(6) Identify the Concept of bisector of two equal chords.
(7) Detect error while proving chords of equal length are at equal distance from the center.
(8) Discuss the proof with other students.
(9) Ask question to know more about the proof.
(10) Observe all aspects of proving chords of equal length are at equal distance from the center
(11) recognize the qualities of exactness and accuracy while drawing perpendicular from center of
Middle point of chord.
(12) Read chart quickly and accurately on proving chords of equal length are equal distance from
the center
3. PRE-REQUISITES : The students have knowledge on congruent triangle ,chord of circle,
perpendicular bisector
TEACHING LEARNING RESOURCES : Usual classroom aids.
LEARNING STRATEGES : Observation ,observing charts and explanation by the teacher.
Classroom interaction procedure Expected pupil responses
4. INTRODUCTION
ACTIVITY -1
When give a diameter find the radius of the circle?
What is Pythagoras theorem?
What do you know about bisector of two equal
chords ?
Through these questions teacher leads the students
to the topic
PRESENTATION
ACTIVITY -2
Teacher draw a figure on black board
In the figure AB and CD are chords of equal length,
OP and OQ are perpendiculars from centre O of the
circle to these chords.
Teacher ask to the students that how can we prove
the result chords of equal length are at equal
distance from the centre.
ACTIVITY -3
Here, these two perpendiculars are from centre of
circle.
So we get AP = ½ AB
CQ= ½ CD (BB)
We know that AB = CD.
So AP= CQ
What can you get from the right angle triangles OAP
and OCQ?
Here OA=OC, teacher ask students that, why
OA=OC?
Also, AP=CQ
I.e., so we get OP²=OQ²
Yes , radius is the half of the diameter
All students responds
Some students respond that, bisector is the
diameter of circle
Pupil replied that the perpendiculars have equal
length
All students respond that perpendicular from
centre bisect the chord
Student respond that inOAP,OP²=OA²-AP²
In OCQ, OQ²=OC²-CQ²
Because OA and OC are radius of the circle.
Classroom interaction procedure Expected pupil responses
5. I.e., OP=OQ so chords of equal length are at equal
distance
From centre
ACTIVITY -4
Suppose AB and CD are not parallel, but they are
chords of equal length, so what we say?
Teacher draws a figure on black board.
(BB)
Since the perpendicular distance from O to lines AB
and CD are equal , the point O is on the bisector of
the angle formed by extending the lines AB and CD
ACTIVITY -5
Teacher explaining with the help of chart
Students respond that perpendicular distance from O
to AB and CD are equal.
Students read carefully and write notes on book.
6. “Chords of equal lengths are at equal
distance from the center.”
Teacher asks students to write proof on note book.
Classroom interaction procedure Expected pupil responses
7. CLOSURE
ACTIVITY-6
Teacher concludes the class by briefly explain the
results of chord of equal length are at equal distance
from the centre.
REVIEW
ACTIVITY -7
Teacher review the lesson by asking certain
questions from the proof.
FOLLOW UPACTIVITY
In a circle of radius 5 cm two chords of lengths
6 cm, 8cm are drawn parallel to each other on either
side of the center .what is the distance between these
chords ?
