Angle2[point, apex, point]
[math]\;\;\;[/math]e.g. Angle2[B,A,C]
returns ∡BAC in the range -π . . . π.
that is, it returns ∡BAC.
tool (.ggt): [url]http://www.geogebratube.org/material/show/id/99838[/url]
__________
An angle has a magnitude and a direction.
Unless explicitly specified, it is always assumed that an magnitude is in the range 0 . . . π.
The direction is [i]always[/i] given by its arrangement in space (geometry). In algebra, we use a sign.
All theorems regarding angles take this for granted.
