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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

344.0. "Triangle with int altitudes" by TOOLS::STAN () Thu Oct 10 1985 16:22

What is the triangle with smallest area that has integer sides
and integer altitudes?
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344.1RAINBO::GRANTFri Oct 11 1985 00:305
With a quick scan of the 2 digit integers, I'd say it's the triangle with 
sides 25, 25, and 30, with altitudes of 16, 16, and 20, and an area of 300.

No proof, since I'm not sure there isn't some skinny triangle with huge sides 
and small area that meets the requirements.  But I'll bet there isn't. 
344.2METOO::YARBROUGHFri Oct 11 1985 11:381
Eh? 16*25/2 = 200, not 300. Maybe you mean 24. That works out.
344.3RAINBO::GRANTMon Oct 14 1985 00:125
Hmm.. yes:  Sides of 25, 25, 30 and altitudes of 24,24 and 20.  Those shorter 
sides have the longer altitudes.

So, is there one with smaller area? This one has an area of 300, as said 
before.
344.4TOOLS::STANFri Oct 18 1985 19:422
But a 15-20-25 right triangle has area of less than that (150),
and its altitudes are integral.
344.5TOOLS::STANSat Oct 19 1985 00:453
I did my own search and found nothing smaller than 150, but, as in the
previously-mentioned search, I can't prove there are no long thin
triangles that I have missed.
344.6TOOLS::STANThu Nov 21 1985 01:204
Peter Gilbert observed that since no altitude can be less than 1,
we need not search any triangle with side larger than 300.
Thus, the search can be limited.  I performed this revised search
and found no smaller triangle.  Thus, the minimal area is indeed 150.