VIDEO: Calculating the area of ​​a circle - Formula and notes on application

The calculation of the circular area for a given radius or diameter

When you need to calculate the area of ​​a circle, you are usually given the radius or diameter. Since the radius always corresponds to half the diameter, you can calculate the area of ​​a circle with a given radius as well as with a given diameter.

• The formula for calculating the area of ​​a circle for a given radius is A = π • r².
• From this, by inserting r = d / 2, the formula for the area for a given diameter can be derived. This reads: A = π • (d / 2)². If you raise the expression in parentheses to the power, you get the formula A = π • d²/ 4, with which you can also calculate the area of ​​the circle.
• The circle constant π, pronounced Pi, is a decimal number with an infinite number of decimal places. You can't replace π with a fraction either. However, the number π is stored on many calculators and is also available in spreadsheet programs. If none of these tools are available to you, it is sufficient to insert a rounded 3.14 for the circle constant.
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• The circle constant has no unit. Accordingly, the unit of the result depends on the unit of the given size. For example, if the radius or diameter is given in centimeters, the area of ​​the circle has the unit cm².


r in a circle - how to calculate the radius

Calculating the diameter or radius in a circle is one of the typical ...

The formula given the scope

It can also be that neither the radius nor the diameter of the circle is given, but instead the circumference.

• Since the circumference of a circle can be calculated with the formula U = π • d or U = π • 2 • r, you can obtain the formula for calculating the circular area for a given by rearranging and inserting Scope.
• The area of ​​a circle can therefore also be calculated using the formula A = U² Calculate / (4 • π).