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coefficient function in sage

asked 2016-06-16 04:00:50 +0200

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I want to compute the coefficient of certain polynomial but he coefficient function in sage gives me back for the coefficient of X^0 that is for any polynomial f f.coefficient(x^0) = 0 Can you some suggest how to change this thing in sage library ?

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Could you please provide an example on how you construct f?

tmonteil gravatar imagetmonteil ( 2016-06-16 11:25:33 +0200 )edit

What does f.coefficients() give you?

calc314 gravatar imagecalc314 ( 2016-06-16 15:20:55 +0200 )edit

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answered 2016-06-20 10:31:17 +0200

slelievre gravatar image

First of all, when you want to use polynomials in Sage, it is always wiser to use elements in some polynomial ring rather than elements of Sage's symbolic ring.

Then, if f is such a polynomial, you can ask for the coefficient of x^k simply by asking f[k]. This works for any k, even if k is larger than the degree of f.

Here is an example.

sage: R.<x> = PolynomialRing(QQ)
sage: f = x^2 - 3
sage: f[0], f[1], f[2], f[3], f[20]
(-3, 0, 1, 0, 0)
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Asked: 2016-06-16 04:00:50 +0200

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Last updated: Jun 20 '16