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CCGPS Geometry Day 20 (9-4-13). UNIT QUESTION: What special properties are found with the parts of a circle? Standard: MMC9-12.G.C.1-5,G.GMD.1-3 Today’s Question: How do we use angle measures to find measures of arcs? Standard: MMC9-12.G.C.2. AGENDA. Notes on Circles
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CCGPS GeometryDay 20 (9-4-13) UNIT QUESTION: What special properties are found with the parts of a circle? Standard: MMC9-12.G.C.1-5,G.GMD.1-3 Today’s Question: How do we use angle measures to find measures of arcs? Standard: MMC9-12.G.C.2
AGENDA • Notes on Circles • Notes on Central Angles • Practice Worksheet • Homework Worksheet
Unit 3 Circles
Segments of Circles
C Parts of a Circle Circle – set of all points _________ from a given point called the _____ of the circle. equidistant C center Symbol:
CHORD: A segment whose endpoints are on the circle
Radius RADIUS: Distance from the center to point on circle P
DIAMETER: Diameter Distance across the circle through its center P Also known as the longest chord.
D = ? 24 32 12 r = ? 16 r = ? 4.5 6 D = ? 12 9
Q R P S T Use P to determine whether each statement is true or false.
Secant Line: intersects the circle at exactly TWO points
Tangent Line: a LINE that intersects the circle exactly ONE time Forms a 90°angle with a radius Point of Tangency: The point where the tangent intersects the circle
Name the term that best describes the notation. Secant Radius Diameter Chord Tangent
Central Section 6.2 Arcs
Central Angle : An Angle whose vertex is at the center of the circle ACB AB A Major Arc Minor Arc More than 180° Less than 180° P To name: use 3 letters C To name: use 2 letters B APB is a Central Angle
EDF Semicircle: An Arc that equals 180° To name: use 3 letters E D P F
THINGS TO KNOW AND REMEMBER ALWAYS A circle has 360 degrees A semicircle has 180 degrees Vertical Angles are Equal
measure of an arc = measure of central angle m AB m ACB m AE A E 96 Q = 96° B C = 264° = 84°
Arc Addition Postulate m ABC = m AB + m BC A C B
m DAB = Tell me the measure of the following arcs. 240 D A 140 260 m BCA = R 40 100 80 C B
CONGRUENT ARCS Congruent Arcs have the same measure and MUST come from the same circle or of congruent circles. C B D 45 45 110 A Arc length is proportional to “r”
Classwork • Practice Worksheet
Homework: • Practice Worksheet