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翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Eccentricity (mathematics) ： ウィキペディア英語版 Eccentricity (mathematics) In mathematics, the eccentricity, denoted ''e'' or $\backslash varepsilon$, is a parameter associated with every conic section. It can be thought of as a measure of how much the conic section deviates from being circular. In particular, *The eccentricity of a circle is zero. *The eccentricity of an ellipse which is not a circle is greater than zero but less than 1. *The eccentricity of a parabola is 1. *The eccentricity of a hyperbola is greater than 1. Furthermore, two conic sections are similar (identically shaped) if and only if they have the same eccentricity. ==Definitions== Any conic section can be defined as the locus of points whose distances to a point (the focus) and a line (the directrix) are in a constant ratio. That ratio is called eccentricity, commonly denoted as ''e''. The eccentricity can also be defined in terms of the intersection of a plane and a double-napped cone associated with the conic section. If the cone is oriented with its axis vertical, the eccentricity is : where β is the angle between the plane and the horizontal and α is the angle between the cone's slant generator and the horizontal. For $\backslash beta=0$ the plane section is a circle, for $\backslash beta=\backslash alpha$ a parabola. (The plane must not meet the vertex of the cone.) The linear eccentricity of an ellipse or hyperbola , denoted ''c'' (or sometimes ''f'' or ''e''), is the distance between its center and either of its two foci. The eccentricity can be defined as the ratio of the linear eccentricity to the semimajor axis ''a'': that is, $e\; =\; \backslash frac$. (Lacking a center the linear eccentricity for parabolas is not defined.) 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Eccentricity (mathematics)」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.