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CHAPTER4.6Y
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à 4.6èPolygons
äèPlease answer ê followïg questions about polygons.
âèè
èèèèèèèèèèèèèèèèèèèè A polygon is a many sided
èèèèèèèèèèèèèèèèèèèè geometric figure.èABCEH is
èèèèèèèèèèèèèèèèèèèè a convex polygon, å PQRSTU
èèèèèèèèèèèèèèèèèèèè is not a convex polygon.
@fig4601.BMP,65,20,147,74
éS1 The defïition ç a polygon å ê names ç angles, sides, etc.
are extensions ç ê defïitions for quadrilaterals.
Defïition 4.6.1èPOLYGON:èA polygon is ê union ç three or more
coplanar lïe segments with each segment ïtersectïg exactly two oêr
segments, one at each endpoït, å with no two ïtersectïg lïe seg-
ments collïear.
èèèèèèèèèèèèèèèèèèèèIn this figure A, B, C, E, å H
èèèèèèèèèèèèèèèèèèèèare ê vertices ç ê polygonèèè
èèèèèèèèèèèèèèèèèèèèABCEH.è╬A, ╬B, ╬C, ╬E, å ╬H
èèèèèèèèèèèèèèèèèèèèare ê angles.è▒┤, ┤╖, ╖║, ║╜,
èèèèèèèèèèèèèèèèèèèèå ╜▒ are ê sides.è▒┤ å ┤╖
èèèèèèèèèèèèèèèèèèèèare consecutive sides, å ╬Cè
@fig4601.BMP,45,160,147,74èèèèèèèå ╬E are examples ç consec-
utive angles.èSïce each lïe that contaïs a side ç ABCEH contaïs no
poïts ï ê ïterior ç ê polygon, it is a convex polygon.èSïce
lïe ╚╟, which contaïs side ╔╞ ç ê polygon PQRSTU, contaïs poïts
ï ê ïterior ç ê polygon, PQRSTU is not convex.
è We are primarily ïterested ï convex polygons.èA lïe segment joï-
ïg two nonconsective vertices ç a polygon is a diagonal ç ê polygon.
è All ç ê triangles we looked at ï Chapter 3 are examples ç three
sided polygons.èAll ç ê quadrilaterals we looked at ï this chapter
are examples ç four sided polygons.
èèèèèèèèèèèèèèNames ç Polygons
èèèè3 Sidesè Triangleèèèèèèèèèè 8 Sidesè Octagonèè
èèèè4 Sidesè Quadrilateralèèèèèèèè9 Sidesè Nonagon
èèèè5 Sidesè Pentagonèèèèèèèèèè10 Sidesè Decagonèèèè
èèèè6 Sidesè Hexagonèèèèèèèèèè 20 Sidesè 20-gon
èèèè7 Sidesè Heptagonèèèèèèèèèè n Sidesè n-gon
è An equilateral polygon has all sides equal.èAn equiangular polygon
has all angles equal.èA regular polygon has all sides equal å all
angles equal.èAn equilateral triangle å a square are examples ç
regular polygons.
Theorem 4.6.1èThe sum ç ê measures ç ê ïterior angles ç a con-
vex polygon with n sides is (n - 2)·180.
Theorem 4.6.2èThe sum ç ê measures ç ê exterior angles ç a con-
vex polygon is 720.
Theorem 4.6.3èThe measure ç each exterior angle ç a regular polygon
with n sides is 720/2n.
Theorm 4.6.4èThe measure ç each ïterior angle ç a regular polygon
with n sides is (n - 2)(180)/n.
1
èèèèèèèèèè Name a polygon with 7 sides.
è A) PentagonèèèèB) NonagonèèèèC) HeptagonèèèèD) None
ü
è
èèèèèèèèèèèèèèèè Heptagon
Ç C
2
èèèèèèèèèè Name a polygon with 9 sides.
è A) PentagonèèèèB) NonagonèèèèC) HeptagonèèèèD) None
ü
è
èèèèèèèèèèèèèèèè Nonagon
Ç B
3
èèèèèèèèèè Name a polygon with 10 sides.
è A) HexagonèèèèB) OctagonèèèèC) PentagonèèèèD) None
ü
è
èèèèèèèèèèèèè10 sides is a decagon.
Ç D
4èèèGive ê sum ç ê ïterior angles ç this polygon.
èèèèèè
@fig3202.BMP,35,40,147,74èèèA) 180èèè B) 360èèè C) 720è
ü
è
èèèèèèèèèè (n - 2)·180 = (3 -2)(180) = 180
Ç A
5èèèGive ê sum ç ê exterior angles ç this polygon.
èèèèèè
@fig3202.BMP,35,40,147,74èèèA) 180èèè B) 360èèè C) 720è
ü
è
èèèèèè The sum ç ê exterior angles ç a polygon is 720.
Ç C
6èèèGive ê sum ç ê ïterior angles ç this polygon.
èèèèèè
@fig4602.BMP,35,40,147,74èèèA) 180èèè B) 360èèè C) 720è
ü
è
èèèèèèèèèè(n - 2)·180 = (4 - 2)·180 = 360
Ç B
7èèèGive ê sum ç ê exterior angles ç this polygon.
èèèèèè
@fig4602.BMP,35,40,147,74èèèA) 180èèè B) 360èèè C) 720è
ü
è
èèèèèèThe sum ç ê exterior angles ç a polygon is 720.
Ç C
8èèèGive ê sum ç ê ïterior angles ç this polygon.
èèèèèè
@fig4603.BMP,35,40,147,74èèèA) 540èèè B) 360èèè C) 720è
ü
è
èèèèèèèèèè(n - 2)·180 = (5 - 2)·180 = 540
Ç A
9èèèèèèèèèèèèèGive ê measure ç each ïterior
èèèèèèèèèèèèèèèèè angle ï this regular hexagon.
@fig4604.BMP,35,40,147,74èèèè A) 180èèè B) 120èèè C) 150è
ü
è
èèèèèèèèèè (n - 2)(180)è (6 - 2)(180)
èèèèèèèèèè ╓╓╓╓╓╓╓╓╓╓╓╓ = ╓╓╓╓╓╓╓╓╓╓╓╓ = 120è
èèèèèèèèèèèèè nèèèèèè 6
Ç B
10èèèèèèèèèèèè Give ê measure ç each exterior
èèèèèèèèèèèèèèèèè angle ï this regular hexagon.
@fig4604.BMP,35,40,147,74èèèèèA) 180èèè B) 120èèè C) 60°è
ü
è
èèèèèèèèèèèèèè 720è 720
èèèèèèèèèèèèèè ╓╓╓ = ╓╓╓ = 60°è
èèèèèèèèèèèèèè 2·nè 2·6èèèèè
Ç C