Let us now identify the [ plane of the triangle ] as the { X-Y Plane } and :
We can then set up a { Z-Axis } perpendicular/orthogonal to the { X-Y Plane } ;
and
This , however , does not mean that we have neglected / forgotten { Triangle A-B-C's in a clockwise rotation order } .
Let us suppose for the moment that we were successful :
so that :
and
as per this set of 3 diagrams immediately below .
Ultimately , these 3 relations below will still hold ,
regardless of whether we are looking in from the { Positive Z } side or alternately from the { Negative Z } side .
vs.
Again we have :
as per the set of 3 diagrams immediately above .
As such :
As a consequent :
THEN :
regardless of what angle-of-rotation we may happen to select .
next .