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POLYGONS

POLYGONS “MANY” “SIDES” A polygon is a 2-dimensional shape. This means that polygons have both length and width. L E N G T H WIDTH Polygons are closed shapes, and they are made of at least 3 line segments. Why is this shape NOT a polygon? This shape is NOT “closed.”

Samuel
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POLYGONS

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  1. POLYGONS “MANY” “SIDES”

  2. A polygon is a 2-dimensional shape.

  3. This means that polygons have both length and width. L E N G T H WIDTH

  4. Polygons are closed shapes, and they are made of at least 3 line segments.

  5. Why is this shape NOT a polygon?

  6. This shape is NOT “closed.”

  7. Why can’t a polygon have only 2 sides?

  8. With only 2 sides, the shape could not be “closed.”

  9. Is this shape a polygon?

  10. As a matter of fact, this IS a polygon.

  11. This shape is “closed,” and it has 12 sides.

  12. However, this is a special type of polygon called “concave.”

  13. It’s called “concave” because some of the sides are “caved in.”

  14. For our purposes, we will be discussing only convex polygons and not concave polygons.

  15. We will learn the names for the first eight polygons.

  16. A one-sided polygon is called…?

  17. That’s a trick question. There is no such thing as a one-sided polygon. Remember, polygons must have at least 3 sides.

  18. A 3-sided polygon is called a triangle.

  19. You can remember the prefix “tri” by thinking of a tricycle. A tricycle has 3 wheels.

  20. A 4-sided polygon is called a quadrilateral.

  21. You can remember the prefix “quad” by thinking “times four.” Quadruple means x 4

  22. A 5-sided polygon is called a pentagon.

  23. You can remember this name by thinking about the building in Washington, D.C.

  24. A six-sided polygon is called a hexagon.

  25. You can remember that a hexagon has six sides because the words hexagon and six both have the letter “x.”

  26. The hexagon is the polygon of choice for bees.

  27. A 7-sided polygon is called a heptagon.

  28. You can remember the prefix “hept” by thinking of the heptathalon in the Olympics. heptathlon—a two-day event in which athletes compete in the 100-meter hurdles, high jump, shot put, and 200-meter dash on the first day and in the long jump, javelin, and 800-meter race on the second day.

  29. Joyner-Kersee, JackieJoyner-Kersee, Jackie (1962- ), American track-and-field athlete, who won the heptathlon event (an all-around event) at the Olympic Games in 1988 and 1992. She is considered one of the greatest female athletes.

  30. An 8-sided polygon is called an octagon.

  31. You can remember the prefix “oct” by thinking of an octopus.

  32. A 9-sided polygon is called a nonagon.

  33. You can remember that a nonagon has nine sides because the words nonagon and nine both have two “ns.”

  34. A 10-sided polygon is called a decagon.

  35. You can remember the prefix “dec” by thinking about a decade. 2000 1999 1998 1997 1996 1995 TEN YEARS 1994 1993 1992 1991

  36. Let’s explore some interesting properties of polygons.

  37. All triangles have a certain characteristic about them.

  38. If you tear off the three corners of any triangle…

  39. If you tear off the three corners of any triangle…

  40. …you can arrange the three angles to form a semicircle.

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