A circle is one of the most interesting geometric shapes but is one of the more difficult ones to understand. Follow these steps to find the area of a circle. You will also learn how to find the area of a sector, which is a slice of a circle, similar to the shape of a slice of pie or pizza.
Area of the circle
Figure out the length of the radius. This may be as simple as dividing the diameter by 2.
Note the formula. The formula for finding the area of a circle is:
Multiply the radius by itself to square it.
Multiply by pi.
If the instructions say "leave in terms of pi", then just stick the pi onto your number.
If the instructions say anything about rounding, replace pi with 3.14 or use your calculator's pi button.
Here is an example:
Occasionally you will see a circle inside of a square. The side length of the square matches the diameter of the circle.
Occasionally you may see a square inside of a circle. The diagonal of the square is also the diameter of the circle.
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