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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

1920.0. "Concours General, France, 1992, problem 2" by BATVX1::ESANU (Au temps pour moi) Fri Dec 16 1994 12:18

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1920.1handwaveWRKSYS::ROTHGeometry is the real life!Fri Dec 16 1994 15:2322
    If you have N points on the unit circle, then to get a stationary
    point of the sum of the pairwise distances between the points,
    a set of relations will have to be satisfied of the form

    for 3 points at angles t1, t2, t3:

	sin(t1 - t2) + sin(t1 - t3) = 0
	sin(t2 - t1) + sin(t2 - t3) = 0
	sin(t3 - t1) + sin(t3 - t2) = 0

    for 4 points at angles t1-t4

	sin(t1 - t2) + sin(t1 - t3) + sin(t1 - t4) = 0;
	sin(t2 - t1) + sin(t2 - t3) + sin(t2 - t4) = 0;
	sin(t3 - t1) + sin(t3 - t2) + sin(t3 - t4) = 0;
	sin(t4 - t1) + sin(t4 - t2) + sin(t4 - t3) = 0;

    and so on, it looks like by symmetry that they should be at the
    vertices of a regular n-gon for at least one solution for case 4 and
    beyond.

    - Jim