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Circles and Circumference. Section 10.1. Circle – set of all ordered points that are equidistant from a given point (center). Chord – segment whose endpoints are points on the circle. Radius – segment with endpoints that are the center and a point of the circle
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Circles and Circumference Section 10.1
Circle – set of all ordered points that are equidistant from a given point (center). • Chord – segment whose endpoints are points on the circle. • Radius – segment with endpoints that are the center and a point of the circle • Diameter – a chord that passes through the center of the circle
Identify Parts of a Circle • Name the circle • Circle A or • Name a radius • Name 2 chords • Name a diameter
All radii in a circle are congruent. • A diameter (d) is composed of 2 radii (r). So all diameters in a circle are congruent. • d = 2r
Find measures in intersecting circles • The diameters of are 10 inches, 20 inches, and 14 inches respectively. Find XB. • d = 10 in circle A, AX = 5 • d = 20 in circle B AB = 10 and BC = 10 • AX + XB = AB • 5 + XB = 10 • XB = 5 • Find BY • d = 14 in circle C, YC = 7 • BY + YC = BC • BY + 7 = 10
Circumference – is the distance around the circle. • Circumference is most represented by C • The ratio of the circumference of a circle and the diameter of the circle is an irrational number called pi. The Greek letter is used as the exact value. • C = • Or C =
Find C if r = 13 inches. • C = • Find C if d = 6 mm • C = • Find d and r if C = • d = 34 • If d = 34 then r = 17