MATHEMATICS NOTES Form 2

MATHEMATICS NOTES Form 2

Booklet 2

_____________________________________________

Ms. G. Bonnici

Name : ___________________________________________ Class: ____________________

- Albert Einstein.

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maths notes booklet 2

Page 1

Circles

At the end of this topic I will be able to:

Understand the meaning of radius, diameter, circumference Find the Circumference of a Circle Find the Area of a Circle Solve problems involving the Circumference and Area of a Circle Work with compound shapes involving circles Find the volume of a Cylinder

Chapter 9, Pg. 172: Circumference and Area of a Circle

The word "circle" derives from the Greek, kirkos coming from the verb `to turn' or `bend'. The circle has been known since before the beginning of recorded history. Natural circles would have been observed, such as the Moon, Sun, and a short plant stalk blowing in the wind on sand, which forms a circle shape in the sand. The circle is the basis for the wheel, which, with related inventions such as gears, makes much of modern civilisation possible. In mathematics, the study of the circle has helped inspire the development of geometry, astronomy, and calculus.

MTH_EN_709_081 Parts of a Circle RLO 1 & 2 Identifying Parts of a Circle

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maths notes booklet 2

Page 2

Investigating the Circle

You will need: 4 circular objects a long string ruler pens and calculator

With your piece of string and a ruler, measure the Circumference and Diameter of each circular object you have got. Make sure you are as accurate as possible. Record your measurements in the table below.

Object

Circumference / cm Diameter / cm

Try to find a relationship between the Circumference and Diameter of each circular object. Conclusion

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maths notes booklet 2

Page 3

The Circumference of a Circle

The circumference of a circle is slightly more than three

times as long as its diameter. The exact ratio is called .

The constant, sometimes written pi, is approximately equal to 3.14159 or . Actually this number is unlike any other number that you have met so far. It cannot be written exactly as a fraction or as a decimal.

This number has been represented by the Greek letter "" since the mid-18th century and now you can also find a button on your calculator.

From your investigation we can conclude that that the Circumference of a Circle can be found by using one of these two formulae:

C = d or C = 2r

Use the button on your calculator

Find the Circumference of a Circle with radius 8.5cm.

Find the Circumference of a Circle with Diameter 34.2cm.

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Find the radius of a circle with Circumference 29.5cm.

Pi Day is celebrated on March 14. The town of Princeton, New Jersey hosts numerous events in a combined celebration of Pi Day and Albert Einstein's birthday, which is also

March 14.

maths notes booklet 2

Page 4

Examples

Find the Perimeter of this shape.

6cm

Find the Perimeter of this shape.

50cm

30cm

Find the Perimeter of this shape. 7cm

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maths notes booklet 2

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