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[[Category:Geometry]]
[[Category:Geometry]]
[[Category:Circles]]
[[Category:Circles]]
Area of a circle is the surface occupied by the circle in a 2-dimensional plane. The area of a circle is given by the formula,
=== Teaching Resource ===
Area of circle = πr<sup>2</sup>, where r is the radius of the circle and constant ratio π = <small><math>{22 \over 7}</math></small>
This area of the circle can be found by two methods-
[[File:Circle-area.png|left|thumb|115x115px|Fig.1. Area of circle]]
# A circle of given radius can be drawn on the graph sheet (Fig.1) and the rough estimate its area can be found by counting the number of squares enclosed.
# By dividing the circle into a number of sectors which when arranged forms a parallelogram. Then the area of the parallelogram(rectangle) gives the area of the circle.(as shown below)
=== Objectives ===
To enable students to-
# understand how the area of a circle can be obtained with the help of area of parallelogram(rectangle);
# derive the formula for the area of circle;
# verify the formula for the various values of the radius.
# solve problems related to area of circle.
=== Prerequisites/Instructions, prior preparations, if any ===
Recall concept of area of a plane figure, circle and its parts.
=== Process (How to do the activity?) ===
==== Teaching Resource ====
{{Geogebra|ywfhqsp5}}
{{Geogebra|ywfhqsp5}}
Geogebra [[:File:Area of circle.ggb]]
Geogebra [[:File:Area of circle.ggb]]
* Identify various given shapes.
* Identify the radius, diameter, sector of the circle.
* What is the relationship between circumference and diameter/radius of a circle?
* Draw a circle and divide it into a number of sectors.
* Show that the sectors when arranged forms a parallelogram(rectangle)
* What is the breadth of the rectangle formed using the sectors of the circle?
* What is the length of the rectangle formed using the sectors of the circle?
* Is the length complete circumference or half circumference of the circle?
* How to find the area of a rectangle?
* Verify for different radii or number of sectors of the circle and analyze the results.
==== Evaluation ====
# Find the area of circular pizza of radius 15 cm.
# If the circumference of a circular sheet is 154m, find its radius. Also find the area of the sheet.