1) The document is a lesson plan for a mathematics class on circle measures, specifically the relationship between the length of an arc and the central angle of the arc. 2) The lesson involves explaining the terms arc length and central angle, presenting the formula that relates arc length to central angle and radius, and working through examples to apply the formula. 3) The learning outcomes are for students to understand and be able to apply the relationship between arc length and central angle, as well as do calculations accurately.

1. LESSON TEMPLATE- II
Name of the teacher : ANCY .T. DAS
Subject : Mathematics
Unit : Circle Measures
Sub Unit : Length and angle
Name of the school : MTGHS,PATHANAPURAM.
Standard : IX G
Strength :40/43
Date :8-12-2016
Time :40 Minutes
CURRICULAR STATEMENT
To understand about length and angle of a circle and its importance in circle measures through
observation, discussion, organization and by analyzing the prepared notes of the pupils.
CONTENT ANALYSIS
Terms : Are of a circle central angle of an arc.
Face : The angle at a point is 360˚.
Concept : The length of an arc of a circle is that fraction of the perimeter as the fraction of 360˚ that its
centre angle is
Formula : Length of an arc = 2πr x
𝑥
360
Symbol : ‘r’ is the radius of the circle and ‘x’ is the central angle of the arc.
Process : Process of finding relationship between length of an arc and central angle of the arc.
PROCESS SKILLS
Observation , finding relationship, comparison, analysis and association.
LEARNING OUTCOMES.
The pupil will be able to
(1) recall the perimeter of a circle.
(2) recognize the term arc length of a circle and central angle of an arc
(3) identify the term arc length and central angle of an arc
(4) explain the relationship between length of an arc of a circle and central angle of an arc.
(5) do oral and written calculations with speed and accuracy.
(6) ask questions to know more about arc length and central angle of an arc
(7) plans to do problems on arc length and central angle of an arc

2. PRE- REQUISITE
Students have knowledge on perimeter of a circle.
TEACHING LEARNING RESOURCES
Usual classroom aids , chart.
LEARNING STRATEGIES
Individual works, observation, explanation by the teacher.
CLASSROOM INTERSCTION PROCEDURE
INTRODUCTION
Activity 1
Teacher enters the class with a pleasant face and
wishes the students.Then check homework
problems and clarify the doubts of the students.
PRESENTATION
Activity 2
Teacher explains
Let A and B be two points on a circle.
A
B
Any part of the circle between the points A and B
are called an arc.
The angle between the two radii joining the ends
of an arc to the centre of the circle is called the
central angle of the arc.
What happened to the length of the arc with
increase in central angle.
EXPECTED PUPIL’S RESPONSE
As the length of the arc increases,measures of
the central angle also increases.

3. Activity 3
Teacher presents a chart before the students.
[ chart
LENGTH ANAD ANGLE
In a circle of radius r,the length of an arc of
central angle x˚ is 2πr x
𝑥
360˚
Or
The length of an arc of a circle is that fraction of
the perimeter as the fraction of 360˚ that its
central angle is.
Activity 4
Teacher gives a question to the students in a
circle of radius 3 cm ,what is the length of an arc
of central angle 60˚
Teacher explains the solution.
Radius of the circle = 3 cm
Central angle of the arc = 60˚
Length of the arc = 2πr x 3 x
60
360
= π cm
= 3.14 cm
Activity 5
Teacher gives another question to the students.
From an iron ring of radius 9 cm, a piece of
central angle 30˚ is cut off. This is bent into a
small circle. What is the radius of the circle ?
Teacher ask the students to solve the problem.
Pupils observe the chart carefully
Pupils listen carefully and write down the notes
Pupils solve the problem.
Radius of the ring = 9 cm
Central angle = 30˚
Length of the arc = 2π x 9 x
30
360
=
3
2
π.
Perimeter of small circle =
3
2
π
Ie,2πr =
3
2
π
r =
3
2×2
= 4 cm

4. CLOSURE
Activity 6
Teacher conclude the class by saying about the
relationship between arc length and central
angle.
REVIEW
Activity 7
Teacher ask questions and clarify the doubts of
the students.
FOLLOW UP ACTIVITY
What is the length of an arc central angle 50˚ in a
circle of radius 2.5 cm ?
Pupils recall
Pupils give the correct answer