Question: Why do I receive "float(undefined)" for the derivate of a piecewise function?

Hello,

I have defined a piecewise function, and then i derive that function and take the arctan of it. However for x=5, which is the maximum x value for the piecewise function, it shows "Float(undefined)".I have attached images at the bottom. I havent been able to figure out why this happens and i would appreciate any help. Also, does somebody know why the following error appears when i try to upload the .mw file? 

Maple Worksheet - Error

Failed to load the worksheet /maplenet/convert/crimp_versuch_tagentenstetig.mw .

Download crimp_versuch_tagentenstetig.mw

 

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