Figure 3.

Frequency distribution of the possible source subtenses of representative angles projected onto a plane (subtenses are shown from 0–180° in 1° increments). (A) The frequency distribution of the possible source subtenses of a representative acute angle (30°) projection. The solid arrow indicates the mean and the open arrow, the median. (B) The frequency distribution of the possible source subtenses of a representative obtuse angle (150°) projection. (C) The frequency distribution of the possible source subtenses of a right-angle projection. Because all angles can project specifically as 0° or 180°, the mean or median subtense of the sources that give rise to a 0° projection is more than the projection itself, and the mean or median subtense of the sources that give rise to a 180° projection is less than the projection itself. These artifacts arise from having made discrete, for practical reasons, the continuous function of angle size. When the source distributions of 0° and 180° projections are plotted in 360° circular space, they are single-peaked symmetrical distributions whose means and medians are in fact 0° and 180°.