Circle Terminology

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GEOMETRY

Circle Terminology

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Radius (or Radii for plural)

The segment joining the center of a circle to a point on the circle.

Example: OA

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Diameter

A chord that passes through the center of a circle.

Example: AB

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Chord

A segment joining two points on a circle

Example: AB

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Chord

A segment joining two points on a circle

Example: AB

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Secant

A line that intersects the circle at exactly two points.

Example: AB

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Secant

A line that intersects the circle at exactly two points.

Example: AB

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Tangent

A line that intersects a circle at exactly one point.

Example: AB

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Central Angle

An angle whose vertex is at the center of a circle.

Example: Angle ABC

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Inscribed Angle

An angle whose vertex is on a circle and whose sides are determined by two chords.

Example: Angle ABC

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Arc

A figure consisting of two points on a circle and all the points on the circle needed to connect them by a single path.

Example: arc AB

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Intercepted Arc

An arc that lies in the interior of an inscribed angle.

Example: arc AC

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Two Intercepted Arc

If angle is inside the circle.

Example: arc AC

arc DF

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If angle is outside the circle.

Example: arc DE

arc DC

Two Intercepted Arc

Slide 15

Investigating Measures of Angles Related to a Circle

Click on GSP 4.00 on the desktop.

Follow the instructions on the handout.