A circle is the set of points equidistant from a given point called the center.   (The degree measure of an entire circle about the center is 360º.)
Notation for circle: circlenotation


* Radii in a circle are congruent (of the same length).


* A diameter is the longest possible chord.

Given circle O:

Arc:   arc a part of a circle's circumference.

Semicircle:   semi
- an arc whose length is exactly half of the circumference (with a corresponding central angle equal to 180º).

Central angles: ∠AOC, ∠DOC, ∠AOJ, ∠DOJ, ∠AOD, ∠COJ
an angle whose vertex is at the center of the circle and whose rays (sides) are radii.


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