Name of the teacher: SINI.S Standard: IX

Name of the school : New .H.S.S. Nellimoodu Division:

Subject : Mathematics Strength:

Unit : Polygons Date :

Subunit : Unchanging Sum Duration: 45 minute

CURRICULAR STATEMENT: Finding the sum of the external angles of any polygon 360.

CONTENT ANALYSIS

Term: External angles.

Facts: 1. Sum of external angles of a polygon is 360.

2. In any polygon, the side is extended and this produces a new angle outside the polygon. This angle is

called an external angle of the polygon.

Concept: The concept of the sum of the external angles of a polygon.

Principle: The sum of the external angles of any polygon is 360.

Process: The process of finding the sum of external angles of a polygon.

Learning outcomes:

Pupil,

1. Remembering information of sum of external angles of the polygons.

2. Develops understanding in finding the sum of external angles of the polygons.

3. Applying the above information in familiar situations.

4. Analyzing the information to explore understandings and relationships.

5. Justifying the above concepts.

6. Creating new ideas related to the above facts and concepts.

7. Develops skills in finding the sum of external angles of the polygons.

8. Develops interest in finding the sum of external angles of the polygons.

Pre-requisites: Polygons, Sum of external angles, Eternal angles.

Teaching learning resources: Models of polygon, Charts.

CLASSROOM INTERACTION PROCEDURE PUPIL RESPONSES

Preparation:

The teacher asked to the students about the polygon.

The teacher asked that What is the formula to finding the sum of

Interior angles of a polygon?

Are polygons having only interior angles?

Give an example of a polygon and draw its figure?

What is an external angle?

Then, draw the external angle?

How to find the external angle of this figure?

We have to find the sum of external angle of this figure?

Development:

The teacher split the students into four groups. Then give some model of

polygons with marked interior angles. The teacher asks to find the external

angles of that. Then it will mark on the chart.

The sum of the angles of an n-sided

polygon is (n-2) x180.

In any polygon, the side is extended

and this produces a new angle outside the

polygon.This angle is called an external angle

of the polygon.

Group Name of polygon External angles Sum of external angles

Then we see that the sum of external angles of any polygon is 360.

To show the slide of it.

Then we see that the sum of external angles of any polygon is 360. To

show the slide of it.

Then show the model based on this concept.

From the working model they clearly understood the concept.

Application:

To check whether the concept is attained to the students teacher

give a problem based on that

To show that the sum of external angle of a regular pentagon is 360.

The teacher asked that to read the question.

What is the sum of interior angle of a regular pentagon?

Name of polygon Sum of external angles

Triangle 360

Quadrilateral 360

Pentagon 360

Hexagon 360

SUM OF EXTERNAL ANGLE OF A POLYGON.

The sum of the external angles of

any polygon is 360.

...

What is one angle of a regular pentagon?

What is the specialty of the external angle of a regular pentagon?

What is one external of a pentagon?

What is the sum of the external angle of a regular pentagon?

Review:

1. How will you find the external angle of a polygon?

2. What is the sum of the external angle of a polygon?

Follow up activity:

1. What is the sum of the external angle of a polygon with side 15?

2. The five angles of a pentagon are 60, 70, 50, 110, 70. Prove that the sum of external angle of this

pentagon is 360?