The atan returns the angle (in radians) of a number, which in my case is in
the rise over run format.
Where either rise, run or both may be negative; the combinations of signs
place the true location of the
angle in +/+, +/- , -/- and -/+ quadrants.

Lacking a proper atan function that preserves the quadrant information;
would one construct if statements
or is there some other (better) way to hande in spreadsheet cell formulas.

TIA
canopy