Circle: Circle Area and Circumference of a
Slide 2: 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.
Slide 3: It works for every single circle in the world FACT
Slide 4: p = 3.14159 26535 89793 23846 26433 83279 50288 41972 ... 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. ``May I have a large container of coffee?''
Slide 5: ``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: The Circle Learning Objective: To find the circumference and area of a circle
Circumference: Circumference Circumference = π × diameter diameter circumference
Area: Area Area = π × radius × radius = π × radius 2 radius area
Slide 9: Circumference is π x diameter π x diameter π x diameter Circumference is π x diameter Area is π r 2
Example 1: Example 1 Circumference = π × diameter 4cm circumference Find the circumference of this circle Circumference = π × 4 = 12·57cm (2 d.p.)
Example 2: Example 2 Circumference = π × diameter circumference Find the circumference of this circle Circumference = π × 16 = 50·27cm (2 d.p.) 8cm
Example 1: Example 1 Area = π × radius × radius 7cm area Find the area of this circle Area = π × 7 × 7 = 153·94cm² (2 d.p.)
Example 2: area Example 2 Area = π × radius × radius Area = π × 5 × 5 = 78·54cm² (2 d.p.) 10cm Find the area of this circle
Question 1: Question 1 Circumference = π × diameter Circumference = π × 9 = 28·27cm (2 d.p.) 9cm Find the circumference and area of this circle Area = π × radius × radius Area = π × 4·5 × 4·5 = 63·62cm² (2 d.p.)
Question 2: Question 2 Circumference = π × diameter Circumference = π × 12 = 37·70cm (2 d.p.) Find the circumference and area of this circle Area = π × radius × radius Area = π × 4·5 × 4·5 = 113·10cm² (2 d.p.) 6 cm