p is the symbol used for this special number Pi is its name (Say it as `pie')
p comes from working with circles.
p is the ratio of the circumference of a circle to its diameter.
This means that you can work out p by dividing distance around a
circle by the length of its diameter.
It works for every single circle in the world
The strange thing is that the answer you get can only ever be approximate that is, you can never have an exact value for pi. This has fascinated
mathematicians for a very long time and they have kept trying to find ways to
calculate values for pi that are more accurate.
p = 3.14159 26535 89793 23846 26433 83279 50288 41972 ...
``May I have a large container of coffee?''
``Now I will a rhyme construct,
By chosen words the young instruct.
Cunningly devised endeavour,
Con it and remember ever.
Widths in circle here you see,
Sketched out in strange obscurity.''
The Circle
Learning Objective:
To find the
circumference and area
of a circle
Circumference
circumference
Circumference =
π × diameter
Area
Area
= π × radius × radius
= π × radius2
area
Example 1
Find the circumference of this circle
circumference
Circumference
= π × diameter
Circumference
=π×4
= 12·57cm (2 d.p.)
Example 2
Find the circumference of this circle
circumference
Circumference
= π × diameter
Circumference
= π × 16
= 50·27cm (2 d.p.)
Example 1
Find the area of this circle
Area
= π × radius × radius
area
Area
= π×7×7
= 153·94cm² (2 d.p.)
Example 2
Find the area of this circle
Area
= π × radius × radius
area
Area
= π×5×5
= 78·54cm² (2 d.p.)
Question 1
Find the circumference and area of this circle
Circumference = π × diameter
Circumference = π × 9
= 28·27cm (2 d.p.)
Area
Area
= π × radius × radius
= π × 4·5 × 4·5
= 63·62cm² (2 d.p.)
Question 2
Find the circumference and area of this circle
Circumference = π × diameter
Circumference = π × 12
= 37·70cm (2 d.p.)
Area
Area
= π × radius × radius
= π × 4·5 × 4·5
= 113·10cm² (2 d.p.)