refresher

definition
A circle is the set of point (locus) equidistant from a given point called the center.   (The measure of an entire circle is 360º.)
Notation for circle: circlenotation
Given circle O:

radiusa

chord

diameter
A diameter is the longest possible chord.

Secant:   secant
- a line passing through two points on
the circle. A secant forms a chord in the interior of the circle.
Warmupcircle

Tangent:  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:   arc
- a part of a circle's circumference.

Minor Arc:  minor
- any arc whose length is less than the length of a semicircle (with a corresponding central angle less than 180º).

Major Arc:  major
- 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:   semi
- 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).


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