Chapter 2
Investigating Geometric Figures
2-2 POLYGONS
Objective: Classify polygons; find
the sum of the measures of the
interior and exterior angles of
polygons
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In the polygons below, an exterior angle has been measured at each vertex. Notice that in each case, the sum of the exterior angle measures is 360°.
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Exterior Angles
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Theorem 2-4
Polygon Exterior Angle-Sum Theorem
The sum of the measures of the
exterior angles of a polygon, one at
each vertex, is 360°.
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4. Find the measure of each exterior angle of a regular 20­gon.
NOTE: One exterior angle of a regular polygon with n
sides = 360
n
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5. Find the value of b in polygon FGHJKL. 6
Ann is making paper stars for party decorations. What is the measure of ∠1?
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Find the measure of each interior angle of pentagon ABCDE. You will have to find the value of c.
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8. The measure of an exterior
angle of a regular polygon is 60°.
Find the number of sides.
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Sum of int <s =
One int < =
Regular
Sum of ext <s =
One ext < = Regular
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pg. 80 # 1­4, 10 – 17, 19 – 26
1. Convex dodecagon
2. Concave decagon
3. Convex octagon
4. Concave pentagon
10. 108;72
11. 140;40
12. 160;20
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13.
14. 5
15. 10 13.
16. 20
17. 19. 102
20. 145
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21. y = 103
22. 103
z = 70
24. 60
23. x = 69
w = 111
25. 113
26. w = 72, x = 59
y = 49, z = 121
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Algebra Review­­Graphing Lines
y = mx + b
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HW # 20
Practice 2­2 Quiz on Thurs.
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