Originally Posted by alejandrito29
in maple signum(x) is |x|/x
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That is incorrect for complex values x. Better is x/|x| which holds for all complex x except zero.
the derivate is d/dx {|x|/x} =signum(1,x)
what is:
signum(1,x,0)
signum(0,x,0)
????
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In Maple, type ?signum to see the help page.
signum(1,x) is the derivative of signum, so it is zero for nonzero real x and undefined otherwise. The optional third argument tells Maple what you want to do with signum(0), some conventions say it should be 0, others that it should be 1, so you could say signum(0,x,0) and signum(0,x,1) for those two signum functions.
