Hiroshi Okumura and Saburou Saitoh,
Harmonic mean and division by zero,
Forum Geometricorum, 18 (2018) 155—159.
Abstract. We examine the harmonic mean from the view point of the division by zero and show that the harmonic mean of a and 0 is 2a or a or zero from several examples. We further show that a result on an Archimedean circle of the arbelos still holds in the singular case by using the method of the division by zero.