Concerning a random triangle on a disk
DR of radius
R in the hyperbolic plane, the following four geometric probabilities are studied: (i) the probability
pa(
R) that a random triangle is acute; (ii) the probability
po(
R) that a random triangle has the orthocenter; (iii) the probability
pe(
R) that a random triangle has at least one of the three excenters; and (iv) the probability
pc(
R) that a random triangle has the circumcenter. It is shown that, as
R tends to the infinity, both the probability
pa(
R) and
po(
R) tend to one, whereas the probability
pe(
R) tends to zero. Moreover it is shown that the probability
pc(
R) tends to a limit
pc, which can be expressed as a certain expectation concerning a random triangle in the Euclidean plane. To evaluate this expectation numerically, we obtain 0.45962039 as an estimate for
pc.
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