The document explains how to calculate the area of a circle, emphasizing the formula A = πr² where r is the radius. It describes the relationship between a circle and a square, noting that the area of a circle is less than that of the surrounding square. Additionally, it provides practical instructions for calculating the area, including various details about the value of pi.

1. Area of a circleArea of a circle

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

3. What about the AREA of a circle?What about the AREA of a 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

4. Finding a
formula for the
area of a circle

5. C = πd or C=2πr
Semi - circle=πr

6. Area of Rectangle= Base x Height
Area = πr x r
Area =πr2

7. 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.

8. 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

9. •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

10. The Summary of The Area of a CircleThe Summary of The Area of a Circle
A circle is defined by its diameter or radius
Diameter
Radius
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 isis an irrational number whose value to 15 decimal places is
ππ = 3.14159265358979.... We usually say= 3.14159265358979.... We usually say ππ ≈≈3.143.14
The area is found
using the formula
A=πr2

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