arctan(y/x) - Wolfram|Alpha
Notice the partial derivative wrt x. Click on 'show steps'. Just in case a picture helps...
... where (key in spoiler) ...
... equals a vector composed of both partial derivatives:gradient of delta(x,y)?
Gradient - Wikipedia, the free encyclopedia
gradient of arctan(y/x) - Wolfram|Alpha
.. as for any vector: the length or magnitude using pythagoras and the direction relative to the x-axis using arctan as we did above for delta.determine the length and direction
For length, simplify
For direction, arctan of a simplification of the 'y' component over the 'x'.
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