en.wikipedia.org/wiki/Area_of_a_circle

In geometry, the area enclosed by a circle of radius r is πr<sup>2</sup>. Here the Greek letter
π represents a constant, approximately equal to 3.14159, which is equal to the
r...

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.khanacademy.org/math/geometry/hs-geo-foundations/hs-geo-area/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.wikihow.com/Calculate-the-Area-of-a-Circle

You will also learn how to find the area of a sector, which is a slice of a circle,
similar in shape to a slice of pie or ... The formula for finding the area of a circle is

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

Did you know that you can figure out the formula for the area of a circle by first
turning the circle into a parallelogram? It seems a little weird, but it really works!

britton.disted.camosun.bc.ca/pi/circlearea/circlearea.html

A circle's area is found using the formula: ... up a circle into little pieces, and then
reassemble it into a shape that we know the area formula for ... the rectangle.

www.regentsprep.org/regents/math/geometry/gp16/circlesectors.htm

Let's review what we know about the area of circles and sectors. ... The second
formula can be algebraically reduced, but it is easier to remember that you are ...

www.1728.org/diamform.htm

Formulas for Circle Circumference, Circle Area, Sphere Area, Partially Filled
Sphere Area, Partially Filled Sphere Volume, Sphere Volume, Cylinder Area, ...

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 ...

math2.org/math/geometry/areasvols.htm

circle = pi r <sup>2</sup>. 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] r<sup>2</sup>.