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Re: [Newbie] Interpreting output


Hi,

f[x_] := Piecewise[{{x^2, x > c}, {x, x <= c}}]

and

D[f[x],x] gives

Piecewise[{{2*x, c - x < 0}, {1, c - x >= 0}}, 0]

as expected

Regards

  Jens

"MC" <daemmerung at enttaeuschung.com> schrieb im 
Newsbeitrag news:d51nl8$cu9$1 at smc.vnet.net...
> Hi everybody....
>
> I'm having troubles in interpreting the output 
> of Mathematica.
>
> My problem is to define a function F(x,y,z) such 
> that:
> F = (whatever) if x>c
> F=(whatever) if x<=c
>
> I achievied this using /;
>
> When I derive F with respect to one of the 
> variables, the result is a mess.
> Just an example with 1 variable:
>
> f=x/;x>0;
> f=-x^2/;x<0;
>
> D[f,x]=-2Condition(1,0)[x^2,x<0]+Condition(1,0)[x^2,x<0]Less(1,0)[x,0]
>
> Even in this very simple case, the result is a 
> real mess:
> I really do not know how should I read 
> that...and I'm wondering if
> I have defined the function in the right way.
>
> Anybody so kind to explain me what's goung on?
>
> Thank you very much for your patience
>
>
> 



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