How many diagonals are there in a polygon having 21 sides?
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Answer:
Step-by-step explanation:
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Know the names of polygons. You may need to first identify how many sides are present in the polygon. Each polygon has a prefix that indicates the number of sides it has. Here are the names of polygons with up to twenty sides:[2]
Quadrilateral/tetragon: 4 sides
Pentagon: 5 sides
Hexagon: 6 sides
Heptagon: 7 sides
Octagon: 8 sides
Nonagon/Enneagon: 9 sides
Decagon: 10 sides
Hendecagon: 11 sides
Dodecagon: 12 sides
Triskaidecagon/tridecagon: 13 sides
Tetrakaidecagon/tetradecagon: 14 sides
Pentadecagon: 15 sides
Hexadecagon: 16 sides
Heptadecagon: 17 sides
Octadecagon: 18 sides
Enneadecagon: 19 sides
Icosagon: 20 sides
Note that a triangle has no diagonals.[3]
Answer:
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Step-by-step explanation:
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