 Basic Circle Information MathBitsNotebook.com Terms of Use   Contact Person: Donna Roberts   A circle is the set of points (locus) equidistant from a given point called the center.   (The measure of an entire circle is 360º.) Notation for circle: Given circle O:   A diameter is the longest possible chord. Secant: - a line passing through two points on the circle. A secant forms a chord in the interior of the circle. Tangent: - a line touching (intersecting) a circle at one point without entering the interior of the circle. Point of Tangency:    point A,  point J,  point D - the point at which a tangent touches (intersects) a circle. Arc: - a part of a circle's circumference. Minor Arc: - any arc whose length is less than the length of a semicircle (with a corresponding central angle less than 180º). Major Arc: - any arc whose length is greater than the length of a semicircle (with a corresponding central angle greater than 180º). Major arc are usually named using three letters to distinguish them from minor arcs. Semicircle: - an arc whose length is exactly half of the circumference (with a corresponding central angle equal to 180º). Radii in a circle are congruent (of the same length). 