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    Re: Mathematical Question
    From: Bill Murdoch
    Date: 2002 Sep 20, 20:46 EDT
    In a message dated 9/19/02 8:33:09 PM Eastern Daylight Time, enoid{at}NUNANET.COM writes:


    What is the term used to describe a small 2 dimensional section of a sphere? Or to put it another way, if a small section of a circle is called an "arc", what is the equivalent in a sphere?


    The length of an arc of a circle is measured in radians.  An arc with the length of its radius has an angle of one radian.  The area of a sphere is measured in steradians.  A spherical surface with an area of its radius squared has a solid angle of one steradian.

    While the arc has only one shape because it is part of a one dimensional closed figure (all arcs differ only in length), the spherical surface could have an infinate number of shapes because it is part of a two dimensional closed figure.  It could be a triangle, square, pentagon, hexagon.... (figures on a spherical surface differ not only in area or solid angle but also in shape).

    Bill Murdoch
       
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