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Geometry Problem

  1. Mar 7, 2005 #1
    what is the minimum length of a shape needed to enclose 4 circles, each with a radius of one?
  2. jcsd
  3. Mar 7, 2005 #2
    How are the circles spaced? Can they overlap at all?
  4. Mar 8, 2005 #3


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    Assuming you have all four circles abutting, so that each is tangent to two others, their centers form a rectangle with sides of length 2. The distance between the centers of diagonally opposite circles is 2√(2). The distance along that diagonal, extended, from the center of such a circle to the outer edge of its circle is, of course, 1 so the distance along that diagonal, from the outer edge of one circle to the outer edge of the other is 2+ 2&radic(2) and that is the diameter of the circle circumscribing all 4. It's radius is 1+ &radic(2). That would have length 2π(1+ √(2)).

    If you are only concerned about a "shape" that includes all four circles, you have a square with "rounded eges". The straight portion of each has length 2 (and there are 4 of those). The rounded portion is a quarter of each circle: length (1/4)(2π)= π/2 and there are four of those: the total length around the four circles is
    8+ 2π.
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