Robert P. Munafo, 2012 Apr 16.
When discussing features around the boundary of a mu-atom (for example, the children of the mu-atom, the two directions one can go in while traveling on the boundary are called clockwise and counterclockwise. The same terms can apply to travel along a lemniscate, and to the order of external angles.
Similarly, three children of R2.1/3a are labeled; in counterclockwise order they are: R2.1/3.1/3a, R2.1/3.1/2a, and R2.1/3.2/3a.
Internal and external angles increase in the counterclockwise direction because that is the standard definition in trigonometry, calculus, etc. It is an arbitrary decision adopted as standard. It is interconnected with another aribtrary choice, putting the square root of minus one "above" the real axis (rather than "below") one choice dictated the other. This is also related to the fact that as you proceed from positive real values to positive imaginary values, to negative real values, the imaginary component of the natural logarithm increases.
revisions: 20080314 oldest on record; 20120416 add illustration
From the Mandelbrot Set Glossary and Encyclopedia, by Robert Munafo, (c) 1987-2017. Mu-ency index
This page was written in the "embarrassingly readable" markup language RHTF, and was last updated on 2017 Feb 02. s.11