Python atan or atan2, what should I use?

Question

The formula f=arctan(ImZ/ReZ) and to implement this, there are two options:

Option 1 (atan):

ImZ=-4.593172163003

ImR=-4.297336384845

>>> z=y/x

>>> f1=math.atan(z)

>>> f1

0.8186613519278327

Option 2 (atan2)

>>> f=math.atan2(y,x)

>>> f

-2.3229313016619604

Why the results different?

Answer 1

Kindly be informed that Atan takes a single argument and Atan2 takes two parameters. The intention of using two parameters instead of one is to collect information on the signs of the inputs in order to return the proper quadrant of the computed angle, which is not achievable for the single-argument Atan.

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