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

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

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.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.varsitytutors.com/hotmath/hotmath_help/topics/area-of-a-circle

The area of a circle is given the formula. A=πr2 . Example 1: What is the area of a circular table with diameter 6 ft? Given that, the diameter of the circular table is ...

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 ...

math2.org/math/geometry/areasvols.htm

circle = pi r 2. ellipse = pi r1 r2 ... [s(s-a)(s-b)(s-c)] when s = (a+b+c)/2 (Heron's formula). regular polygon ... (total area) = perimeter(b) L + 2b. sphere = 4 [pi] r2.