The meaning of 'adjacent arcs' and how their arc lengths can be added.
Math Open Reference

Definition and properties of a sector  a pieshaped part of a circle..
Math Open Reference

Gives examples of problems with intercepted arc, central angle, and angles inside and outside the circle.
Online Math Learning

Discusses the properties of chords and inscribed angles of a circle and their geometric relationships. Includes a brief worksheet.
Algebra Lab

Finding the radius of an arc or segment given its height and width.
Math Open Reference

Difference between major and minor arcs. How they can be ambiguous.
Math Open Reference

Definition of arc length and formula to calculate it from the radius and central angle of the arc.
Math Open Reference

Shows how a central angle can intercept or 'cut off' an arc
Math Open Reference

Definition and properties of an arc
Math Open Reference

An interactive page that lets you drag the arc and it shows the minor arc measure.
mathWarehouse
