Arc Arrow 1
The arc is oriented. It respects the equivalence of these three statements:
Arc BC subtends central angle BAC,
There is a one-to-one correspondence between points on arc BC and points on segment BC.
The arc respects minimum rotation.
We may then preserve measure:
|BC| (magnitude) is the distance from B to C (direction).
|∡BAC| (magnitude) is the angle from B to C (direction/sign).