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Polygons |
| Objective
Classify polygons. Find the angle sums of polygons. |
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Vocabulary
polygon, pentagon, hexagon, octagon, regular polygon, heptagon, nonagon, decagon |
| A polygon is a closed geometric figure whose sides are segments.. A polygon is named according to the number of its sides. A regular polygon sides have the same length and all of its angles have the same measure. |
| To find the sum (s) of the measures of the angles of a polygon, we can divide a polygon into triangles by using diagonals from one vertex. The number of triangles you can divide a polygon into is 2 less than the number of sides it has. We can use a formula to find the sum of the measures of the angles of a polygon of n sides. ****** s = (n-2) X 180º |
| Quadrilateral
4 sides s = (4-2) 180 s = 2 * 180º = 360º
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Pentagon
5 sides s = (5-2) 180 s = 3 * 180º = 540º |
Hexagon
6 sides s = (6-2) 180 s = 4 * 180º = 720º |
| Triangle
3 sides |
Quadrilateral
4 sides |
Pentagon
5 sides |
| Hexagon
6 sides |
Heptagon
7 sides |
Octagon
8 sides |
| Nonagon
9 sides |
Decagon
10 sides |
| Name each polygon. Find the sum of the measures of the angles. |
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| Find the degree measure of x in each polygon. |
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Remember to ask Ms Painter for password. |
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| 1) Pentagon
s = (5-2) 180 s = 3 * 180 s = 540º |
2) Quadrilateral
s = (4-2) 180 s = 2 * 180 s = 360º |
3) Hexagon
s = (6-2) 180 s = 4 * 180 s = 720º |
| 4)
s = (4-2) 180 s = 2 * 180 s = 360 138 + 59 + 138 = 335 360 - 335 = 25º x = 25º |
5)
s = (5-2) 180 s = 3 * 180 s = 540 120 + 120 + 110 + 90 = 440 540 - 440 = 100º x = 100º |
6)
s = (6-2) 180 s = 4 * 180 s = 720 150 + 150 + 60 + 150 + 60 = 570 720 - 570 = 150º x = 150º |
