en.wikipedia.org/wiki/Area_of_a_circle

In geometry, the **area** enclosed by a **circle** of radius r is π r^{2}. 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

This relationship is expressed in the following **formula**: diam_formula.gif . **circle**
grid The **area** of a **circle** is the number of square units inside that **circle**. If each ...

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

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.purplemath.com/modules/sectors.htm

Explains **formulas for areas** of sectors of **circles** and lengths of arcs.
Demonstrates how to use the **formulas** in each of degrees and radians.

www.mathwords.com/a/area_sector_circle.htm

**Area** of a Sector of a **Circle**. The **formula** is given below. ... Mathwords: Terms and
**Formulas** from Algebra I to Calculus written, illustrated, and webmastered by ...

www.math.com/tables/geometry/circles.htm

arc: a curved line that is part of the circumference of a **circle** ... **Area of Circle**
Sector: (with central angle theta ) ... **Equation** of **Circle**: (Cartesian coordinates)