"Area of Circle" Presentation

Area of a circleArea of a circle

TThe AREA of a circle?he AREA of a circle?2r

2rr

To find the area of a circle, first consider a square…

The area of this square

in terms of r (radius) is…

A= 2r x 2r = 4r2

What about the AREA of a What about the AREA of a circle?circle?2r

2r

Now think about a circle inside the square…

The area of the circle must be less than the area of the square…

A < 4r2

r

Area = ? xr2

Finding a formula for the area of a circle

C = πd or C=2πrSemi - circle=πr

Area of Rectangle= Base x Height

Area = πr x r

Area =πr2

Summary: How to Calculate the Area of the circle

1= Figure out the length of the radius. This

may be as simple as dividing the diameter by 2.

2= Note the formula. The formula for finding

the area of a circle is:

Here I present a short instruction of the practical use of the “Pie" formula. The instructions I wrote here are based on a short problem from our Math’s Workbook.

3= Multiply the radius by itself to square it. 4= Multiply by pie.

>> If the instructions say "leave in terms of pie”, then just stick the pie onto your number.

>> If the instructions say anything about rounding, replace pi with 3.14 or use your calculator's pi button.

Here is an example:

Summary: How to Calculate the Area of the circle

•Occasionally you will see a circle inside of a square. The side length of the square matches the diameter of the circle.

•Occasionally you may see a square inside of a circle. The diagonal of the square is also the diameter of the circle.

Summary: How to Calculate the Area of the circle

The Summary of The Area of a The Summary of The Area of a CircleCircle

A circle is defined by its diameter or radius

Diameter

Rad

ius The perimeter or circumference of a circle

is the distance around the outside

The area of a circle is the space inside it

The ratio of π (pi)diameter

ncecircumfere

ππ is an irrational number whose value to 15 decimal places is an irrational number whose value to 15 decimal places isis

ππ = 3.14159265358979.... We usually say = 3.14159265358979.... We usually say ππ ≈≈3.143.14 The area is found

using the formula

A=πr2

By Filip Car 8MP.S. If you have any feedback, feel free to contact me by fcar@bisb.sk or just give it to me in class