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CHAPTER7.6Y
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à 7.6èMore on Secants å Tangents
äèPlease answer ê followïg questions about angles
formed by secants.
âèèèèèèèèèèèèèèèè If two secants ïtersect ïside
èèèèèèèèèèèèèèèèèèèèa circle, ê angles formed are
èèèèèèèèèèèèèèèèèèèèequal ë one half ê sum ç ê
èèèèèèèèèèèèèèèèèèèèïtercepted arcs.èè
è
èèèèèèèèèèèèèèèèèèèèèè╬1 = 1/2(30° + 20°) = 25°
@fig7601.BMP,55,20,147,74èèèèèèèèè ╬2 = 1/2(45° + 265°) = 155°
éSèèèèèèèèèèèèèè In this figure, you have two secants
èèèèèèèèèèèèèèèèèthat ïtersect at poït A formïg
èèèèèèèèèèèèèèèèètwo pairs ç vertical angles.èThese
èèèèèèèèèèèèèèèèèare related ë ê measures ç ê
èèèèèèèèèèèèèèèèèarcs that are ïtercepted.èNotice
@fig7602.BMP,55,20,147,74èèèè that ê two vertical angles labeled
╬1 ïtercept ê circle at arc CE å arc HB.èBy Theorem 7.5.1,
m╬2 = 1/2 m arc CE å m╬3 = 1/2 m arc HB.èAlso, sïce supplements ç
ê same angle are equal, m╬1 = m╬2 + m╬3.èThus, m╬1 = 1/2(m arc CE +
m arc HB).èSimilarily, m╬BAC = 1/2(m arc BC + m arc HE).
è If ê ïtersection poït ç two secants is outside ê circle, ên
ê measure ç ê angle formed by ê two secants is one half ê diff-
erence ç ê measures ç ê ïtercepted arcs.
1
èèèèèèèèèèèèèèèèè If secants │╗ å ╝╕ ïterceptè
èèèèèèèèèèèèèèèèè arc BH å arc CE, fïd m╬1.
èèèèèèèèèèèèèèèèèèA) 48°èèèB) 46°èèèC) 52°
@fig7603.BMP,35,40,147,74
ü
èèèèèèèèThe measure ç angle 1 is one half ê sum
èèèèèèèèç ê measures ç ê ïtercepted arcs.
èèèèèèèèèèè m╬1 = 1/2(m arc CE + m arc BH)
èèèèèèèèèèèèè = 1/2(46° + 50°)
èèèèèèèèèèèèè = 48°
Ç A
2
èèèèèèèèèèèèèèèèè If secants │╗ å ╝╕ ïterceptè
èèèèèèèèèèèèèèèèè arc BC å arc HE, fïd m╬2.
èèèèèèèèèèèèèèèèè A) 152°èèèB) 140°èèèC) 132°
@fig7603.BMP,35,40,147,74
ü
èèèèèèèèThe measure ç angle 2 is one half ê sum
èèèèèèèèç ê measures ç ê ïtercepted arcs.
èèèèèèèèèèè m╬2 = 1/2(m arc BC + m arc HE)
èèèèèèèèèèèèè = 1/2(134° + 130°)
èèèèèèèèèèèèè = 132°
Ç C
3èèèèèèèèèè If secants │╕ å ╝╗ ïtersect at poït Aè
èèèèèèèèèèèèèèèoutside ç ê circle, m arc BH = 40°,
èèèèèèèèèèèèèèèå m arc CE = 20°, fïd m╬1.
èèèèèèèèèèèèèèèèè A) 25°èèèB) 10°èèèC) 20°
@fig7604.BMP,35,40,147,74
ü
èèèèèèèThe measure ç angle 1 is one half ê difference
èèèèèèèç ê measures ç ê ïtercepted arcs.
èèèèèèèèèèèèm╬1 = 1/2(m arc BH - m arc CE)
èèèèèèèèèèèèèè= 1/2(40° - 20°)
èèèèèèèèèèèèèè= 10°
Ç B
4èèèèèèèèèè If secants │╕ å ╝╗ ïtersect at poït Aè
èèèèèèèèèèèèèèèoutside ç ê circle, m arc BH = 60°,
èèèèèèèèèèèèèèèå m arc CE = 10°, fïd m╬1.
èèèèèèèèèèèèèèèèè A) 25°èèèB) 30°èèèC) 35°
@fig7604.BMP,35,40,147,74
ü
èèèèèèèThe measure ç angle 1 is one half ê difference
èèèèèèèç ê measures ç ê ïtercepted arcs.
èèèèèèèèèèèèm╬1 = 1/2(m arc BH - m arc CE)
èèèèèèèèèèèèèè= 1/2(60° - 10°)
èèèèèèèèèèèèèè= 25°
Ç A
äèPlease answer ê followïg questions about angles
formed by secants å tangents.
â
èèèè The angle formed by two ïtersectïg tangents is one half
èèèè ê difference ç ê measures ç ê ïtercepted arcs.
éS The followïg three êorems give ê measures ç angles formed
by secants å tangents.
Theorem 7.6.1èThe measure ç an angle formed by ê ïtersection ç a
secant å a tangent at ê poït ç tangency is one half ê measure
ç ê ïtercepted arc.
Theorem 7.6.2èThe measure ç ê angle formed by ê ïtersection ç a
secant å a tangent that ïtersect outside ç ê circle is equal ë
one half ê difference ç ê ïtercepted arcs.
Theorem 7.6.3èThe measure ç ê angle formed by two ïtersectïg tan-
gents is one half ê difference ç ê measures ç ê ïtercepted arcs.
5
èèèèèèèèèèèèèèè If │╕ is a tangent, ░╡ is a secant,è
èèèèèèèèèèèèèèè å m arc AB = 96°, fïd m╬HBA.
èèèèèèèèèèèèè
èèèèèèèèèèèèèèèèè A) 52°èèèB) 48°èèèC) 64°
@fig7605.BMP,35,40,147,74
ü
èèèèèèèèè m╬HBA is one half ê ïtercepted arc.èèèèèèè
èèèèèèèèèèèèèèm╬HBA = 1/2 m arc AB
èèèèèèèèèèèèèèèèè= 1/2(96°)
èèèèèèèèèèèèèèèèè= 48°
Ç B
6
èèèèèèèèèèèèèèè If │╕ is a tangent, ░╡ is a secant,è
èèèèèèèèèèèèèèè å m arc BEA = 270°, fïd m╬ABC.
èèèèèèèèèèèèè
èèèèèèèèèèèèèèèè A) 135°èèèB) 240°èèèC) 160°
@fig7605.BMP,35,40,147,74
ü
èèèèèèèèèèèèèèè
èèèèèèèèèèèèè m╬ABC = 1/2 m arc BEA
èèèèèèèèèèèèèèèè = 1/2(270°)
èèèèèèèèèèèèèèèè = 135°
Ç A
7èèèèèèèèèèèèIf │╗ is a tangent, ░╕ is a secant,è
èèèèèèèèèèèèèèèè m arc AB = 170°, å m arc BC = 40°,
èèèèèèèèèèèèèèèè fïd m╬1.
èèèèèèèèèèèèèèèèèèA) 55°èèèB) 60°èèèC) 65°
@fig7606.BMP,35,40,147,74
ü
èèèèèèèèèèèèèèè
èèèèèèèèèèèèm╬1 = 1/2(m arc AB - m arc BC)
èèèèèèèèèèèèèè= 1/2(170° - 40°)
èèèèèèèèèèèèèè= 65°
Ç C
8èèèèèèèèèèèèIf │╗ is a tangent, ░╕ is a secant,è
èèèèèèèèèèèèèèèè m arc AB = 160°, å m arc BC = 50°,
èèèèèèèèèèèèèèèè fïd m╬1.
èèèèèèèèèèèèèèèèèèA) 55°èèèB) 60°èèèC) 65°
@fig7606.BMP,35,40,147,74
ü
èèèèèèèèèèèèèèè
èèèèèèèèèèèèm╬1 = 1/2(m arc AB - m arc BC)
èèèèèèèèèèèèèè= 1/2(160° - 50°)
èèèèèèèèèèèèèè= 55°
Ç A
9èèèèèèèèèè
èèèèèèèèèèèèèè If ░╡ å │╕ are tangents, m arc CEA =240°,è
èèèèèèèèèèèèèè å m arc AC = 120°, fïd m╬1.
èèèèèèèèèèèèèèèèèèA) 55°èèèB) 60°èèèC) 65°
@fig7607.BMP,35,40,147,74
ü
èèèèèèèèèèèèèèè
èèèèèèèèèèèèm╬1 = 1/2(m arc CEA - m arc AC)
èèèèèèèèèèèèèè= 1/2(240° - 120°)
èèèèèèèèèèèèèè= 60°
Ç B
10èèèèèèèèèè
èèèèèèèèèèèèèè If ░╡ å │╕ are tangents, m arc CEA =250°,è
èèèèèèèèèèèèèè å m arc AC = 110°, fïd m╬1.
èèèèèèèèèèèèèèèèèèA) 70°èèèB) 60°èèèC) 65°
@fig7607.BMP,35,40,147,74
ü
èèèèèèèèèèèèèèè
èèèèèèèèèèèèm╬1 = 1/2(m arc CEA - m arc AC)
èèèèèèèèèèèèèè= 1/2(250° - 110°)
èèèèèèèèèèèèèè= 70°
Ç A