en.wikipedia.org/wiki/Area_of_a_circle

In geometry, the area enclosed by a circle of radius r is πr2. Here the Greek letter π represents a constant, approximately equal to 3.14159, which is equal to the ratio of the circumference of any circle to its diameter. One method of deriving this formula, which originated with Archimedes, ...

www.mathgoodies.com/lessons/vol2/circle_area.html

Area of a circle is presented in this interactive lesson from Math Goodies. ... In the last lesson, we learned that the formula for circumference of a circle is: C ...

www.mathwarehouse.com/geometry/circle/area-of-circle.php

Area of a circle, formula for area explained with examples, pictures, interactive examples and quiz.

www.khanacademy.org/math/basic-geo/basic-geo-area-and-perimeter/area-circumference-circle/v/area-of-a-circle

The area of a circle is pi times the radius squared (A = π r²). Learn how to use this formula to find the area of a circle when given the diameter.

www.virtualnerd.com/pre-algebra/perimeter-area-volume/circles/circle-sector-area-examples/circle-area-from-diameter

www.mathsisfun.com/geometry/circle-area.html

Area of a Circle. Calculator Enter the radius, diameter, circumference or area of a Circle to find the other three. The calculations are done "live":.

www.wikihow.com/Calculate-the-Area-of-a-Circle

A common problem in geometry class is to have you calculate the area of a circle based on provided information. You need to know the formula for finding the ...

math.tutorvista.com/geometry/area-of-circle.html

Area of a circle can be found easily with the help of the area of a circle formula if the radius or diameter (twice of radius) of the circle is given. In this article, we ...

www.bbc.co.uk/schools/gcsebitesize/maths/geometry/circlesrev3.shtml

Area of a circle. There is only one formula for the area of a circle: A = π r2. We must therefore remember to use the radius each time. Question. Find the area of a ...