->   Angle = ATAN (p / q)
In BASIC, ATN (the arc-tangent function) produces an answer in the range
pi/2 to -pi/2. So, at the very least, you'll have to add something to
the program to deal with the negative values, and map them on to the
range from pi/2 to pi.
I think it's quicker just to subtract two ATNs, appropriately expressed.
                             dow
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