# Tangents, Arcs and chords, basic terms Section 9-1.

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Tangents, Arcs and chords, basic terms Section 9-1

Circle Circle- The set of points in a plane at a given distance from a given point in that plane.

Center Center- The given point (C) in the middle of a circle. C

Radius Radius- The given distance between the center and circumference of a circle. C

Chord Chord- A segment whose endpoints lie on a circle. C

Secant Secant- A line that contains a chord. C

Diameter Diameter- A chord that contains the center of a circle. C

Tangent Tangent- A line in the plane of a circle that intersects the circle in exactly one point. C T

Point of Tangency Point of Tangency- The point (T)where a tangent intersects a circle. C T

Sphere Sphere- A sphere with center O and radius R is the set of all points in space at a distance R from point O

Congruent Circles (or spheres)- Congruent Circles (or spheres)- Circles (or spheres) that have congruent radii. C 3 D 3

Concentric Circles Concentric Circles- Circles that lie in the same plane and have the same center. C

Concentric Spheres Concentric Spheres- Spheres that have the same center.

Inscribed/Circumscribed Inscribed- A polygon is inscribed in a circle when each vertex of the polygon lies on the circle. Circumscribed- A circle is circumscribed about the polygon when each vertex of the polygon lies on the circle.

Inscribed/Circumscribed