# An Archi gif, compliments to Lucas V. Barbosa

Given the last weblog on radians, I noticed that Wikipedia had a nice gif animation created by Lucas V. Barbosa. The article even mentions: “This is a featured picture on the English language Wikipedia and is considered one of the finest images.” Barbosa even made a version with tau = 2 pi. The latter is less appealing since it does not mention pi, while, of course, tau reads like radius *r*, and then can cause confusion (indeed, run that gif too).

It appears that Barbosa put his gif into the public domain. Thus I adapted it for Archi = Θ = 2 π, including a note of reference that he did most of the creative work.

Interestingly, Barbosa’s original gif has a small shaded disc in the center. If we take the radius of the larger circle as *r *= 1 then we get the smaller Angular Circle in the center with *r = *1 / Θ and circumference 1. My proposal is to speak about “angles” on the Angular Circle (use α and β), and to use “arc” for the radians on the Unit Circle (use φ and ψ). Of course, angles as measured on the Angular Circle are arcs too, but it helps being able to say that angles add up to 1 Turn and Unit Circle arcs to 1 Archi rad.

PM. The Wikipedia article I referred to has a wrong statement on dimensions (today, July 2014). For a discussion of this, see the earlier weblog entry on radians.