[Search for users] [Overall Top Noters] [List of all Conferences] [Download this site]

Conference rusure::math

Title:Mathematics at DEC
Moderator:RUSURE::EDP
Created:Mon Feb 03 1986
Last Modified:Fri Jun 06 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:2083
Total number of notes:14613

1459.0. "circle triplets." by CADSYS::COOPER (Topher Cooper) Mon Jun 17 1991 14:27

    The article mentioned in note 1456.8 ends with a description of an open
    problem in planar disections.  Since it is one of those problems where
    the question is easily stated and easy to understand, I thought I would
    post it.

    "Can you cut a circular disc into three pieces which, apart from rigid
    motions, are identical?  It is easy to do this if overlaps are allowed
    or for a disc with its central point missing."

					Topher
T.RTitleUserPersonal
Name
DateLines
1459.1is this meant to use a program to solve?SMAUG::ABBASIWed Jun 19 1991 02:1713
    i think it is hard to this without a computer program, where you
    try different cutting/glue back different combinations of pieces
    untill to get 3 pieces identical, i assum offcourse we are allowed
    to glue back different pieces in the process.
    this is then some what similar to problems where you are asked to
    end up with certine quantity of liquid in one container of some size
    given you have one or more empty containers on the side to use.
    this is easy to see through the whole process if the number of STEPS
    is small (around 10), but if one has to do many hundreds of steps,
    i cant see how to do this other by brute forces search method.
    
    /nasser
    
1459.2No program will workAGOUTL::BELDINPull us together, not apartWed Jun 19 1991 13:149
    No, the "point" is that the center can only be in "one" of the three
    sections.  So the normal pie-shaped segments won't work, because they
    all intersect at the center.  This (like many of the counter-intuitive
    problems) is a topological problem.  Such problems require very careful
    attention to what you do with the boundaries of the pieces and so on. 
    No digital computer program has enough precision to handle these
    issues.  The techniques used are pure mathematical reasoning.
    
    Dick
1459.3I can do it almost everywhere ...DECWET::BISHOPF. Avery Bishop, back in the US for nowMon Jun 24 1991 20:2612
>    No, the "point" is that the center can only be in "one" of the three
>    sections.  So the normal pie-shaped segments won't work, because they
>    all intersect at the center.  This (like many of the counter-intuitive
>    problems) is a topological problem.  Such problems require very careful
>    attention to what you do with the boundaries of the pieces and so on. 
>    No digital computer program has enough precision to handle these
>    issues.  The techniques used are pure mathematical reasoning.
 
	But what's a set of measure zero among friends?

	-fab