Polygon Angles and Theorems

Section 3-5
Angles of a Polygon
 
many
 
two
 
endpoint
 
collinear
 
Yes
 
Yes
 
Yes
 
No
 
No
 
No
 
angles
 
a
 
the
 
polygon
 
Yes
 
Yes
 
No
 
No
 
point
 
in
 
interior
 
of
 
the
  Number of Sides
 
Name of Polygon
 
3
 
4
 
5
 
6
 
7
 
8
 
9
 
10
 
n
 
triangle
 
hexagon
 
octagon
 
decagon
 
n-gon
 
pentagon
 
quadrilateral
 
heptagon
 
nonagon
 
consecutive
 
vertices
 
C   D  E
 
B   C  D
 
A   E  D
 
E   A  B
 
A   B  C
 
D   C  B
 
two     nonconsecutive
 
vertices
Theorem 3-13
The sum of the measures of the
angles of a convex polygon with n
sides is _____________________.
 
(n – 2) 180
1.  What is the interior angle sum of a decagon?  _____
2.  What is the interior angle sum of an octagon? _____
3.  What is the interior angle sum of 22-gon? ________
 
(n – 2)180
 
(10 – 2)180
 
(8)180
 
1440°
 
(n – 2)180
 
(8 – 2)180
 
(6)180
 
1080°
 
(n – 2)180
 
(22 – 2)180
 
(20)180
 
3600°
Theorem 3-14
The sum of the measures of the exterior angles
of any convex polygon, one angle at each vertex,
is __________.
 
360°
4.  What is the exterior angle sum of a pentagon?
_______________________
5.  What is the exterior angle sum of a decagon?
_______________________
 
360°
 
360°
Regular Polygon
 – a polygon that is both
____________ and ________________.
6.  What is the measure of one interior angle of
a regular hexagon?
 
__________
7.  What is the measure of one interior angle of
a regular pentagon?
 
_____________________
 
equilateral
 
equiangular
 
120°
 
108°
8.  What is the measure of one interior angle of
a regular decagon?  ____________________
 
144°
9.  What is the measure of one exterior angle of
a regular hexagon? _______________________
10.  What is the measure of one exterior angle
of a regular octagon? _____________________
 
60°
 
45°
11.  What polygon has an exterior angle
measuring 24°?
 
______________________
12.  What polygon has an interior angle
measuring 135°? ______________________
 
15-gon
 
24n = 360
 
n = 15
 
octagon
 
(n – 2)180 = 135n
 
– 360 = –45n
 
8 = n
Complete with 
always, sometimes,
 or 
never
.
13.  The sum of the measures of the exterior
angles of any polygon, one angle at each vertex,
is __________ 360°.
14.  The sum of the measures of the angles of a
convex polygon is ______________ 360°.
15.  A segment joining two vertices of a polygon
is ________________ a diagonal.
 
always
 
sometimes
 
sometimes
16.  The sum of the measures of the exterior
angles of a polygon _____________ depends on
the number of sides of the polygon.
17.  A regular polygon is __________ equilateral.
18.  An equiangular polygon is _________
regular.
 
never
 
always
 
sometimes
19.  Three of the angles of a quadrilateral have
measures 90, 60, and 115.  The fourth angle has
measure________.
 
95°
 
90 + 60 + 115 + x = 360
 
(4 – 2) 180 = 360
HOMEWORK:
page 104 #2-22 even
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Explore the angles of polygons, including interior and exterior angle sums, theorems 3-13 and 3-14, properties of regular polygons, and measurements of angles in various polygon types. Discover the relationships between sides, vertices, and angles to deepen your geometric knowledge.

  • Polygons
  • Geometry
  • Angles
  • Theorems
  • Regular Polygons

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  1. Section 3-5 Angles of a Polygon

  2. many angles two endpoint collinear Yes Yes No No No Yes

  3. a point of in the polygon interior the Yes No Yes No

  4. Number of Sides 3 4 5 6 7 8 9 10 n Name of Polygon triangle quadrilateral pentagon hexagon heptagon octagon nonagon decagon n-gon

  5. consecutive vertices C D E A E D E A B A B C B C D D C B

  6. two nonconsecutive vertices

  7. Theorem 3-13 The sum of the measures of the angles of a convex polygon with n sides is _____________________. (n 2) 180

  8. 1440 1. What is the interior angle sum of a decagon? _____ (n 2)180 (10 2)180 (8)180 1080 2. What is the interior angle sum of an octagon? _____ (n 2)180 (8 2)180 (6)180 3600 3. What is the interior angle sum of 22-gon? ________ (n 2)180 (22 2)180 (20)180

  9. Theorem 3-14 The sum of the measures of the exterior angles of any convex polygon, one angle at each vertex, is __________. 360

  10. 4. What is the exterior angle sum of a pentagon? _______________________ 360 5. What is the exterior angle sum of a decagon? _______________________ 360

  11. Regular Polygon a polygon that is both ____________ and ________________. equilateral equiangular 6. What is the measure of one interior angle of a regular hexagon? __________ 120 ? 2 180 ? 6 2 180 6 angle = angle = 7. What is the measure of one interior angle of a regular pentagon? _____________________ ? 2 180 ? angle = 108 5 2 180 5 angle =

  12. 8. What is the measure of one interior angle of a regular decagon? ____________________ 144 ? 2 180 ? 10 2 180 10 angle = angle =

  13. 9. What is the measure of one exterior angle of a regular hexagon? _______________________ angle = 360 ? 60 angle = 360 6 10. What is the measure of one exterior angle of a regular octagon? _____________________ angle = 360 ? 45 angle = 360 8

  14. 11. What polygon has an exterior angle measuring 24 ? ______________________ 15-gon 24 1 = 360 24n = 360 n = 15 angle = 360 24 = 360 ? ? ? 12. What polygon has an interior angle measuring 135 ? ______________________ ? 2 180 ? 135 = (n 2)180 = 135n octagon ? 2 180 ? angle = 135 1 = ? 2 180 ? 360 = 45n 8 = n

  15. Complete with always, sometimes, or never. 13. The sum of the measures of the exterior angles of any polygon, one angle at each vertex, is __________ 360 . always 14. The sum of the measures of the angles of a convex polygon is ______________ 360 . sometimes 15. A segment joining two vertices of a polygon is ________________ a diagonal. sometimes

  16. 16. The sum of the measures of the exterior angles of a polygon _____________ depends on the number of sides of the polygon. never always 17. A regular polygon is __________ equilateral. sometimes 18. An equiangular polygon is _________ regular.

  17. 19. Three of the angles of a quadrilateral have measures 90, 60, and 115. The fourth angle has measure________. 95 (4 2) 180 = 360 90 + 60 + 115 + x = 360

  18. HOMEWORK: page 104 #2-22 even

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