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I'm new to Mathematica and I'm trying to obtain a minimax rational function approximation to a certain expression. In particular, I'm using

mma = MiniMaxApproximation[x^2, {x, {8, 10}, 2, 2}]

Unfortunately, Mathematica 7 replies with the same expression I'm trying to calculate, namely

MiniMaxApproximation[x^2, {x, {8, 10}, 2, 2}]

Of course, I'm aware this is a very simple test, since x^2 is the rational function approximation of itself.

I'm also trying other possibilities like RationalInterpolation, EconomizedRationalApproximation etc., but none is working. Only PadeApproximant returns a result.

Anyone has an idea on why this happens?

Thank you very much in advance.

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Did you load the package that defines the function using Needs["FunctionApproximations`"]? – Szabolcs Feb 1 at 16:28
this works : MiniMaxApproximation[x^2 + 0.000001 Sin[x], {x, {8, 10}, 2, 2}] – andre Feb 1 at 17:29
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answered over here.. stackoverflow.com/questions/14650207/… – george2079 Feb 1 at 18:32
after loading the package you will find minmax doesnt like it when you request a numerator of the same order as the polynomial expressions,..x^2, {x , {8,10},1,2} works – george2079 Feb 1 at 18:37
Thanks to Szabolcs and george who have spot my mistake. – JackOLantern Feb 2 at 7:03

closed as too localized by J. M.♦ Apr 27 at 4:49

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