2024-09-08 Sunday Sign in CN

Activities
Heron triangles and the hunt for unicorns
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Reporter:
Andrew N. W. Hone, University of Kent
Inviter:
Xiangke Chang, Associate Professor
Subject:
Heron triangles and the hunt for unicorns
Time and place:
10:00-11:00 July 6 (Saturday), N202
Abstract:

A Heron triangle is one that has all integer side lengths and integer area, which takes its name from Heron of Alexandria's area formula. From a more relaxed point of view, if rescaling is allowed, then one can define a Heron triangle to be one whose side lengths  and area are all rational numbers. A perfect triangle is a Heron triangle with all three medians being rational. According to a longstanding conjecture, no such triangle exists, so perfect triangles are as rare as unicorns. However, if perfect is the enemy  of good, then perhaps it is best to insist on only two of the medians being rational. Buchholz and Rathbun found an infinite family of Heron triangles with two rational medians, which they were able to associate with the set of rational points on an elliptic  curve E(Q). Here we describe a recently discovered explicit formula for the sides, area and medians of these (almost perfect) triangles, expressed in terms of a pair of integer sequences: these are Somos sequences, which first became popular thanks to David  Gale's column in Mathematical Intelligencer.