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Circle has infinite sides how many sides does a semi circle have?

  1. Oct 11, 2008 #1
    If a circle has infinite sides how many sides does a semi circle have?
    i have asked my teachers at school but they have ll said u wud have 2 divide infinity by 2 and +1 which obviously isnt possible cos infinity isnt reli a number is it...

  2. jcsd
  3. Oct 11, 2008 #2
    Re: Circles!!!

    A circle is said to have infinitely many "sides" due to the analogy with regular polygons.
    (i.e. a triangle has 3, a square 4, and so on)
    Eventually you get a shape with so many sides that it "becomes" a circle.
    If you want to find how many "sides" a semicircle has, just continue in the same way...
    Cut regular polygons in half and work out how many sides they have
    (i.e. half a triangle has 3 sides half a square has 4, half a pentagon.... etc)

    Do you see the idea?

    (It's just a bad/weird definition of a circle, since it doesn't really have sides, does it?)
  4. Oct 11, 2008 #3
    Re: Circles!!!

    Any curve can be looked at as having an infinite number of 'sides' whose length goes to zero, no matter how big.
  5. Oct 11, 2008 #4


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    Re: Circles!!!

    there are two sides to a circle - inside and outside. (posted lest someone begin to take this more seriously than the topic deserves)
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