Åk 6–9

3.5 Circle
There are a number of concepts connected to circles.  It is a good idea to know them.

 Center This point is exactly in the middle of the circle. Radius A line from the center point to a point on the circle’s arc. The segment is abbreviated r and is the same as half the diameter. Cord A segment between two points on the circle. A cord does not have to go through the center point. Diameter A segment between two points on a circle which goes through the center point. Can be abbreviated d. Circle Arc A continuous length of a part of the circle’s circumference. Circular segment An area which is limited by a circle’s arc and a cord between the arc’s endpoints. Circle Sector
An area which is which is limited by a circle’s arc and radiuses to the arcs end points.

 Area = p · r2 · v 360 The Circle’s Area and Circumference The Circle’s Area Can be defined as the measure of the surface within the circle’s arc. Area = p · r2 The Circle’s Circumference Can be defined as the measure of the circle’s arc. Circumference = p · 2r = p · d   Inscribed circle Circumscribed circle