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Circles. Yes I know we did this yesterday. Circumference. Posh name for the perimeter of a circle Measured in normal units of length cm etc. But how do I work it out?. Glad you asked. First we need to remember the basics. diameter. Radius pl. radii. Get to the point.
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Circles Yes I know we did this yesterday
Circumference • Posh name for the perimeter of a circle • Measured in normal units of length cm etc. • But how do I work it out?
Glad you asked. • First we need to remember the basics diameter Radius pl. radii
Get to the point. Circumference = 2πr (r = radius) = πd (d = diameter) π (‘pi’) = 3.1416……… (goes on forever) Yes just like someone else
One for you to try C = 2 x π x r = 2 x π x 6 = 12 π = 37.7cm (to 1 d.p.) 6cm
So what about area? • Measured in ‘square units’ • Area = πr2 (π x radius x radius)
Example Area = π x 52 = 25π = 78.5 cm2 (to 1 d.p.) 5cm