Li Zhou, Do dogs know the bifurcation locus?,
Forum Geometricorum, 17 (2017) 45--46.

Abstract. A dog runs at speed r and swims at speed s, with r > s. For a fixed point A in a lake with a straight shoreline, where are all the points B in the lake such that the direct swimming path from A to B takes the dog the same time as the fastest indirect swimming- running-swimming path? We give a simple geometric solution to this bifurcation-locus problem.

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