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LESSON 11.2 CHORDS AND ARCS. OBJECTIVE: To use chords, arcs and central angles to solve problems To recognize properties of lines through the center of a circle. Label each picture as a chord, arc or a central angle:. x . central angle. arc. chord. Theorem 11.4.
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LESSON 11.2 CHORDS AND ARCS OBJECTIVE: To use chords, arcs and central angles to solve problems To recognize properties of lines through the center of a circle
Label each picture as a chord, arc or a central angle: x central angle arc chord
Theorem 11.4 Within one circle or within (two or more) congruent circles: central angles have chords (1) chordshave arcs (2) arcs have central angles (3)
BC PF Example #1: In the diagram, circle O circle D. Given that BC PF, what can you conclude? And why (theorem)? P B F D O C Theorem: arcs have ’s O D AND Theorem: ’s have chords
Theorem 11.5 Within one circle or within (2 or more congruent circles): (Biconditional) If chords are equidistant from the (1) they are . center of a circle, then (2) If two or more chords are , then they are equidistant from the center.
AB CD A F EG FG B AB CD EG FG G D C E IF THEN THEN IF
Ex. #2 Find a. Give reason (theorem). a and PR are equidistant from center. So, they are 25 un. Therefore, a = THEOREM If chordsareequidistant from the center of the Circle, then they are .
Theorem 11.6 In a circle, if a diameter is perpendicular to a chord, then it bisects the chord and its arcs. THEN IF
Theorem 11.7 In a circle, if a diameter bisects a chord (that is not another diameter) then it is perpendicular to the chord. THEN IF
A A B B Theorem 11.8 In a circle, if a segment is the perpendicular bisector of a chord, then it contains the center of a circle THEN AB passes through the center of the circle. IF
Ex. #3 Find r. State the reason (theorem). If KN were extended, it would be a diameter and it is to LM. Therefore, it bisects LM. So, LN = 7. Why? r2 = 72 + 32 r2 = 49 + 9 If a diameter is to a chord then it bisects the chord. r2 = 58 r = 58
Ex. #4 Find y. State the reason (theorem) Is this a right triangle? Why? Yes. If a diameter bisects a chord then it is to the chord. 152 = y2 + 112 225 = y2 + 121 104 = y2 2 26 = y
ASSIGNMENT: Page 593 #1 – 16 Write out the theorem used for #3-16