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・ Polynomial basis
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Polynomial lemniscate
・ Polynomial long division
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・ Polynomial remainder theorem
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・ Polynomial signal processing
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Polynomial lemniscate : ウィキペディア英語版
Polynomial lemniscate

In mathematics, a polynomial lemniscate or ''polynomial level curve'' is a plane algebraic curve of degree 2n, constructed from a polynomial ''p'' with complex coefficients of degree ''n''.
For any such polynomial ''p'' and positive real number ''c'', we may define a set of complex numbers by |p(z)| = c. This set of numbers may be equated to points in the real Cartesian plane, leading to an algebraic curve ''ƒ''(''x'', ''y'') = ''c''2 of degree 2''n'', which results from expanding out p(z) \bar p(\bar z) in terms of ''z'' = ''x'' + ''iy''.
When ''p'' is a polynomial of degree 1 then the resulting curve is simply a circle whose center is the zero of ''p''. When ''p'' is a polynomial of degree 2 then the curve is a Cassini oval.
== Erdős lemniscate ==

A conjecture of Erdős which has attracted considerable interest concerns the maximum length of a polynomial lemniscate ''ƒ''(''x'', ''y'') = 1 of degree 2''n'' when ''p'' is monic, which Erdős conjectured was attained when ''p''(''z'') = z''n'' − 1.
This is still not proved but Fryntov and Nazarov proved that ''p'' gives a
local maximum.〔
〕 In the case when ''n'' = 2, the Erdős lemniscate is the Lemniscate of Bernoulli
:(x^2+y^2)^2=2(x^2-y^2)\,
and it has been proven that this is indeed the maximal length in degree four. The Erdős lemniscate has three ordinary ''n''-fold points, one of which is at the origin, and a genus of (''n'' − 1)(''n'' − 2)/2. By inverting the Erdős lemniscate in the unit circle, one obtains a nonsingular curve of degree ''n''.

抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)
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