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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

210.0. "Triangle of triangles" by TAV02::NITSAN () Thu Jan 17 1985 03:43

I saw this one long ago:  Given ANY triangle, find a way to partition it
(is this the correct English word?) into triangles with "sharp" angles
(LESS than 90 deg.) ONLY. What's the minimum number of triangles?
                                                                  NITSAN
T.RTitleUserPersonal
Name
DateLines
210.1HARE::STANThu Jan 17 1985 04:123
"partition" is a good word.

"acute" would be better for "sharp".
210.2METOO::YARBROUGHThu Jan 17 1985 17:047
I believe the number is seven. It's hard to display here, but maybe I can
give a clear verbal description.
There is at most one obtuse angle. Contruct a pentagon with one side in the
middle of the long edge opposite the obtuse angle, one side on each edge
joining at that angle, and the last two sides connecting the loose ends.
Join the five corners of the pentagon near the middle. The construction is 
quite loose and the points can always be chosen so that all angles are <90.