Question: Quantum mech Levinson's theorem and arctan function

Hello everybody . I have a problem with plotting a trig function : arctan(x)

I would live to plot 

In the plot ,the angle jump from -pi/2(-1,57) to pi/2 (1,57)and for u-> there is an asymptot in delta=0

But instead this the asymptote that I would like to see is in delta= -3pi.

How can I remove the discontinuity of the arctan function and plot continuos negative angle?

Thank's and best regards

Please Wait...