Re: Function Programming Problems
- To: mathgroup at smc.vnet.net
- Subject: [mg90809] Re: [mg90782] Function Programming Problems
- From: Sseziwa Mukasa <mukasa at jeol.com>
- Date: Fri, 25 Jul 2008 06:12:53 -0400 (EDT)
- References: <200807240851.EAA18893@smc.vnet.net>
On Jul 24, 2008, at 4:51 AM, davey79 at gmail.com wrote:
> Hello,
>
> A colleague and myself are working on some Mathematica labs for
> Calculus using Mathematica 6.0 and I can't seem to find any
> information or examples that explain defining functions and using
> functions as arguments.
>
> I want to define a LinearApproximation command that preferably would
> take two arguments and return the linear approximation. Ideally,
>
> LinearApproximation[function_,a_] would have
> LinearApproximation[Sin[x],0] give "x" as the output.
>
> So far I have:
> LinearApproximation[function_, a_, x_] := function[a] +
> function'[a]*(x - a)
>
> which works mostly nicely, except it only works with
> LinearApproximation[Sin,0,x].
>
> Does anyone know how I would fix this to allow Sin[x] as input (or
> even x^2, etc)? Getting rid of the third argument "x" would be nice,
> but not necessary.
Sin[x] is not a function in Mathematica, Sin[#]& or Function[{x},Sin
[x]] are functions, you can pass them as arguments, so
LinearApproximation[Sin[#]&,a,x]
works, as does
LinearApproximation[#^2&,a,x]
Two other notes; first Mathematica will simplify the resulting
polynomials so you may not get the exact results you expected,
secondly for built in functions of a single argument the expression
LinearApproximation[Sin, a, x]
is also allowed as shorthand.
Finally, Mathematica already has a function for series expansion
called Series which you may want to look at.
Regards,
Ssezi
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