Circle+Features

this is circle features []


 * ** :  ** ||
 * [[image:http://www.coolmath.com/reference/images/circle1.gif width="136" height="136" caption="circle graphic"]] || ** The radius of a circle is the distance from the center of the circle to the outside edge. ** ||
 * [[image:http://www.coolmath.com/reference/images/line-red.gif width="600" height="2" caption="red line"]] ||


 * ** :  ** ||
 * [[image:http://www.coolmath.com/reference/images/circle2.gif width="136" height="136" caption="circle graphic"]] || ** The diameter of a circle is longest distance across a circle. (The diameter cuts through the center of the circle. This is what makes it the longest distance.) ** ||
 * [[image:http://www.coolmath.com/reference/images/line-red.gif width="600" height="2" caption="red line"]] ||

|||| **  (the perimeter of a circle):  ** || where r = the radius of the circle and pi = 3.141592... ** ||
 * [[image:http://www.coolmath.com/reference/images/circle3.gif width="139" height="138" caption="circle graphic"]] || ** The circumference of a circle is the perimeter -- the distance around the outer edge. ** ** Circumference = [[image:http://www.coolmath.com/reference/images/circle4.gif width="63" height="27" caption="circle graphic"]]
 * [[image:http://www.coolmath.com/reference/images/line-red.gif width="600" height="2" caption="red line"]] ||

where r = the radius of the circle and pi = 3.141592... ** ||
 * ** :  ** ||
 * [[image:http://www.coolmath.com/reference/images/circle3.gif width="139" height="138" caption="circle graphic"]] || ** Area   = [[image:http://www.coolmath.com/reference/images/circle5.gif width="57" height="32" caption="circle graphic"]]
 * [[image:http://www.coolmath.com/reference/images/line-red.gif width="600" height="2" caption="red line"]] ||

|||| ** :  ** || (The diameter is a chord -- it's just the longest chord!) ** || || |||| ** :  ** || ** Arc Length   =   ** || |||| ** :  ** || |||| ** :  ** || ** Sector Area   =   ** ||
 * [[image:http://www.coolmath.com/reference/images/circle6.gif width="139" height="136" caption="circle graphic"]] || ** A chord of a circle is a line segment that connects one point on the edge of the circle with another point on the circle.
 * [[image:http://www.coolmath.com/reference/images/circle7.gif width="139" height="150" caption="circle graphic"]] || ** An arc of a circle is a segment of the circumference of the circle. ** ||
 * [[image:http://www.coolmath.com/reference/images/line-red.gif width="900" height="2" caption="red line"]] ||
 * ** :  ** ||
 * [[image:http://www.coolmath.com/reference/images/circle8.gif width="137" height="136" caption="circle graphic"]] || ** Arc length of a circle in radians: ** ** Arc Length   = [[image:http://www.coolmath.com/reference/images/circle10.gif width="40" height="32" caption="circle graphic"]]  **
 * Arc length of a circle in degrees: **
 * [[image:http://www.coolmath.com/reference/images/line-red.gif width="900" height="2" caption="red line"]] ||
 * [[image:http://www.coolmath.com/reference/images/circle10-5.gif width="137" height="136" caption="circle graphic"]] || ** A sector of a circle is a pie shaped portion of the area of the circle. Technically, the piece of pie is between two segments coming out of the center of the circle. ** ||
 * [[image:http://www.coolmath.com/reference/images/line-red.gif width="900" height="2" caption="red line"]] ||
 * [[image:http://www.coolmath.com/reference/images/circle11.gif width="137" height="136" caption="circle graphic"]] || ** Sector area of a circle in radians: ** ** Sector Area   = [[image:http://www.coolmath.com/reference/images/circle13.gif width="64" height="45" caption="circle graphic"]]  **
 * Sector area of a circle in degrees: **


 * ~ []

Terms ||~ Definitions ||
 * Circle || Set of all points equidistant from a given point ||
 * Radius || A segment whose endpoints are the center and any point on the circle ||
 * Chord || A segment whose endpoints are on a circle. ||
 * Diameter || A chord that passes through the center of the circle. ||
 * Tangent || A line that intersects the circle in exactly one point. ||
 * Point of Tangency || The point where a tangent line intersects the circle. ||
 * Tangent circles || Two circles that intersect each other in only one point. ||
 * Common tangent || A line that is tangent to two coplanar circles. ||
 * Concentric Circles || Two circles that share the same center. ||
 * Congruent Circles || Two circles that have the same radius. ||
 * Center || A circle is named by this point. ||
 * Central Angle || An angle whose vertex is the center of the circle. ||
 * Minor arc || An arc of a circle whose measure is less than 180 degrees. ||
 * Major arc || An arc of a circle whose measure is greater than 180 degrees. ||
 * Semicircle || An arc of a circle whose measure is equal to 180 degrees. ||
 * Inscribed Angle || An angle whose vertex is on a circle and whose sides extend through the circle. ||
 * Intercepted arc || The arc that lies in the interior of an angle. ||
 * Secant || A line that intersects a circle at two points. ||