 Lesson 10.1a Circle Terminology.

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Lesson 10.1a Circle Terminology

Circle Definition Circle :
The set of coplanar points equidistant from a given point. The given point is called the CENTER of the circle. The distance from the center to the circle is called the RADIUS. Center Radius

Definitions Chord : The segment whose endpoints lie on the circle.
Diameter : A chord that contains the center of the circle. Tangent : A line in the plane of the circle that intersects the circle in exactly one point. Tangent Point of Tangency : Chord The point where the tangent line intersects the circle. Diameter Secant : A line that contains a chord. Secant

Example: In the following figure identify the chords, radii, and diameters.
B F C E Radii: Diameter:

Definitions Congruent Circles : Concentric circles :
Circles that have congruent radii. 2 2 Concentric circles : Circles that lie in the same plane and have the same center.

Polygons Inscribed Polygon:
A polygon inside the circle whose vertices lie on the circle. Circumscribed Polygon : A polygon whose sides are tangent to a circle.

ARCS Arcs : The part or portion on the circle from some point B to C is called an arc. A B C Example: B Semicircle: An arc that is equal to 180°. O A Example: C

Minor Arc & Major Arc Minor Arc :
A minor arc is an arc that is less than 180° A minor arc is named using its endpoints with an “arc” above. A Example: Major Arc: A major arc is an arc that is greater than 180°. B B O A major arc is named using its endpoints along with another point on the arc (in order). A Example: C

Example: ARCS Minor Arc: Major Arc: Semicircle:
Identify a minor arc, a major arc, and a semicircle, given that is a diameter. Minor Arc: A C D E F Major Arc: Semicircle: