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How To Create An Arc Of A Circle As A Straight Line?

  1. May 21, 2013 #1
    How do you construct the arc of the circle as a straight line by geometry not by an equation?

    Thank you
  2. jcsd
  3. May 21, 2013 #2


    Staff: Mentor

    You can't. An arc of a circle is not a straight line. The geometrical way to construct a circle is to use a compass, which is not the same as the compass that is used to determine magnetic north. The compass I'm referring to has two legs that are hinged. One leg has a sharp point, and the other has a pencil or pen.

    The end with the point is fixed, and the other end is used to draw the circle.
  4. May 21, 2013 #3
    Of course, you can : First, buy a compass with infinitely long legs. Then, go to the infinity. There put the sharp point and turn the compass : Very far from there, the straight arc is drawn. :devil:
    Last edited: May 21, 2013
  5. May 21, 2013 #4


    User Avatar
    Homework Helper

    mymachine might be asking how to construct a line [itex]2\pi r[/itex] units long given the circle with radius r.

    I don't believe it can be done because of a similar argument for why you cannot square the unit circle - i.e. to find a square with side length [itex]\sqrt{\pi}[/itex] by geometric constructions.
  6. May 21, 2013 #5


    Staff: Mentor

    Where do you buy one of these?
  7. May 21, 2013 #6
    You may ask Alice. She knows a good shop in Wonderland.
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