The Circle and Some Related Terms

**Circle**–The set of all points in a plane at a given distance from a given point.The set of all point equidistant from a given point called the center of the circle.

The given point is the

*center of the circle*and the given distance is the*radius.*

**Radius**–It is defined as a segment connecting the center with a point on the circle. (radii –plural)**Chord**–A segment whose endpoints lie on the circle.**Diameter**–A chord that contains the center of the circle.__Not all chords__can be a diameter.It divides a circle into two congruent arcs called semicircles

**Arc**–A portion of a circle where two distinct points on a circle divides the circle into two parts.Two distinct points on a circle divide the circle into parts called

*arcs*.

**3 Classifications of Arcs****Minor Arc**–Less than 180 degrees**Major Arc**–Greater than 180 degrees**Semicircle**–Exactly 180 degrees

**Tangent Line**–A tangent to a circle is a line, coplanar with the circle that intersects the circle in exactly one point.**Secant Line**–A secant line is a line that intersects the circle in two points. It is always composed of a*chord.***Exterior of the circle**–It is a set of points in the plane of the circle whose distance from the center is greater than the radius.The circle is divided into 3 parts:

*Exterior, Interior and the circle itself*

**Central Angle**–It is an angle in the plane of the circle whose vertex is the center of the circle.**Inscribed Angle**–An angle whose vertex lies on the circles and whose sides contain points of the circle.**Inscribed Polygon**–It is a polygon whose sides are chords of a circle. The polygon is inscribed in a circle, and the circle is circumscribed about the polygon.**Circumscribed Polygon**–The polygon is outside the circle.**Common Tangent**–It is a tangent to each of coplanar lines.**Common External Tangent**–The line did not intersect the center of the circle**Concentric Circles**–Two or more circles with the same center.**Congruent Circles**–The circles have the same radius.

**Circle**–The set of all points in a plane at a given distance from a given point.The set of all point equidistant from a given point called the center of the circle.

The given point is the

*center of the circle*and the given distance is the*radius.*

**Radius**–It is defined as a segment connecting the center with a point on the circle. (radii –plural)**Chord**–A segment whose endpoints lie on the circle.**Diameter**–A chord that contains the center of the circle.__Not all chords__can be a diameter.It divides a circle into two congruent arcs called semicircles

**Arc**–A portion of a circle where two distinct points on a circle divides the circle into two parts.Two distinct points on a circle divide the circle into parts called

*arcs*.

**3 Classifications of Arcs****Minor Arc**–Less than 180 degrees**Major Arc**–Greater than 180 degrees**Semicircle**–Exactly 180 degrees

**Tangent Line**–A tangent to a circle is a line, coplanar with the circle that intersects the circle in exactly one point.**Secant Line**–A secant line is a line that intersects the circle in two points. It is always composed of a*chord.***Exterior of the circle**–It is a set of points in the plane of the circle whose distance from the center is greater than the radius.The circle is divided into 3 parts:

*Exterior, Interior and the circle itself*

**Central Angle**–It is an angle in the plane of the circle whose vertex is the center of the circle.**Inscribed Angle**–An angle whose vertex lies on the circles and whose sides contain points of the circle.**Inscribed Polygon**–It is a polygon whose sides are chords of a circle. The polygon is inscribed in a circle, and the circle is circumscribed about the polygon.**Circumscribed Polygon**–The polygon is outside the circle.**Common Tangent**–It is a tangent to each of coplanar lines.**Common External Tangent**–The line did not intersect the center of the circle**Concentric Circles**–Two or more circles with the same center.**Congruent Circles**–The circles have the same radius.