# area of a circle

## Calculus area_circle

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### Function : area_circle

#### Summary :

area online calculator that can calculate the area of a circle from its radius or from its diameter.

area_circle online

#### Description :

The calculator has several features allowing it to make surface calculations. It is thus possible to calculate the surface of a circle, also called area of a disc through area_circle function, but also the surface of a rectangle , or the surface of a square (which is a particular rectangle).

Calculating the area of a circle can be done from its radius or its diameter.

# Calculating the area of a circle from its radius

The area of a circle is the area bounded by the circle. The area of a circle is given by the formula pi*r^2 where r represents the radius of the circle.

Thus, calculating the area of a circle with radius 3 is done by typing the following formula area_circle(3) , after calculation, the result 9pi is returned.

It is also possible to make symbolic calculation and calculate the area of a circle with radius 1+x, by typing the following formula area_circle(1+x) , after calculation, the result is returned.

# Calculating the area of a circle from its diameter

If d is the diameter of the circle and its radius r, then the radius of a circle is equal to half of its diameter which is expressed by the formula r=d/2. From this formula, it is possible to determine the area of a circle from its diameter.

The area of a circle can be calculated from its diameter using the formula pi*(d/2)^2, where d is the diameter of the circle.

Thus, calculating the area of circle with diameter 5 is done by entering the following formula area_circle(5/2) , after calculation, the result 25/4*pi is returned.

area online calculator that can calculate the area of a circle from its radius or from its diameter.

#### Syntax :

area_circle(3) returns 9pi