# CP Geometry Mr. Gallo

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CP Geometry Mr. Gallo
```CP Geometry
Mr. Gallo
Shapes for the next page. Draw all the diagonals possible from only one
vertex. Use the information in the chart on the next page.
Find the measures of the interior angles of the following
polygons. Complete the table below. Use the shapes on the
previous page.
Sum of Interior
Angle Measures
Polygon
# of Sides
# of s Formed
4
2
2*180=360
Pentagon
5
3
3*180=540
Hexagon
6
4
4*180=720
Heptagon
7
5
5*180=900
Octagon
8
6
6*180=1080
Polygon Angle-Sum Theorem
 The sum of the measures of the interior angles of an n-gon
is:
 n  2 180
Examples:
Find the sum of the measures of the following polygons:
a). Decagon
b). 15-gon
c). dodecagon
Complete Got It? #1 p. 353
10  2 180  8*180  1440
15  2 180  13*180  2340
12  2 180  10*180  1800
a. 2700
b. 1980 ÷ 180 + 2 = 13 sides
Find the value of x in each polygon.
V
122°
U 121°
117°
T
W
x°
120 118 117 121 122  mW  720
598  mW  720
mW  122
120° R
118°
S
86 118 129  82  mR  540
415  mR  540
mR  125
Q
82°
P 129°
x°
118°
T
86°
S
R
Types of Polygons
Equilateral Polygon
Equiangular Polygon
Regular Polygon
Corollary to the Polygon Angle-Sum Theorem
The measure of each interior angle of a regular n-gon is:
 n  2 180
n
Complete Got It? #2 p. 354
9 − 2 180
7 180
=
= 140°
9
9
Exteriors Angle of a Polygon
Find the sum of the exterior angles, one from each
vertex of the following polygons.
90°
90°
86°
94°
115°
65°
110° 70°
75°
16°
164°
86 110 164  360
100°
80°
90  115  80  105  360
Polygon Exterior Angle Sum Theorem
 The sum of the measures of the exterior angles of a
polygon, one at each vertex, is 360°.
m1  m2  m3  m4  m5  360
2
1
3
5
4
Complete Got It? #4 p. 355
360
= 40°
9
Homework: p. 356 #18-25, 29-36, 41
```
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