Area of a circle

P=\pi r^2

Result unit: area units

What it describes

The area of a disk of radius

r

P

area of the circle

r

radius

The area of a circle grows with the square of the radius — doubling the radius quadruples the area.

Areas of circular figures, cross-sections, bases of a cylinder and a cone.

The radius of a circle is

r=3

. Find the area.

Substitution

r=3

Result

P=\pi\cdot9=9\pi\approx28.3

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