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Re: how to replace...?



Yacine Ait-Sahalia, writes
> What should I do to systematically replace the limit
>         (f[y]-f[x])/(y-x) /. y->x
> by f'[x], no matter what the function f is?

Yacine:

Unprotect[Limit];

Limit[(f_[y_]-f_[x_])/(y_-x_), y_->x_]:= f'[x]

Limit[(f[y]-f[x])/(y-x), y->x]

f'[x]
--
Allan Hayes
Mathematica Training and Consulting
Leicester UK
http://www.haystack.demon.co.uk
hay@haystack.demon.co.uk
voice: +44 (0)116 271 4198
fax: +44(0)116 271 8642




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