Circles
For a circle: radius \(r\) is half the diameter \(d\). Circumference (C) and area (A) are given by:
\( C = 2\pi r \)
\( A = \pi r^2 \)
Example
Example: Circle with radius 5 → Circumference = \(2\pi \times 5 = 10\pi\), Area = \(\pi \times 5^2 = 25\pi\)
Practice
Lvl 2
The area of a circle is \(36\pi\) cm². Work out the perimeter (circumference) of the circle. Give your answer in terms of \(\pi\).
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