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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 Fermat's spiral ： ウィキペディア英語版 Fermat's spiral Fermat's spiral (also known as a parabolic spiral) follows the equation :$r\; =\; \backslash pm\backslash theta^\backslash ,$ in polar coordinates (the more general Fermat's spiral follows ''r'' 2 = ''a'' 2''θ''.) It is a type of Archimedean spiral. In disc phyllotaxis, as in the sunflower and daisy, the mesh of spirals occurs in Fibonacci numbers because divergence (angle of succession in a single spiral arrangement) approaches the golden ratio. The shape of the spirals depends on the growth of the elements generated sequentially. In mature-disc phyllotaxis, when all the elements are the same size, the shape of the spirals is that of Fermat spirals—ideally. That is because Fermat's spiral traverses equal annuli in equal turns. The full model proposed by H Vogel in 1979〔 〕 is :$r\; =\; c\; \backslash sqrt,$ :$\backslash theta\; =\; n\; \backslash times\; 137.508^\backslash circ,$ where ''θ'' is the angle, ''r'' is the radius or distance from the center, and ''n'' is the index number of the floret and ''c'' is a constant scaling factor. The angle 137.508° is the golden angle which is approximated by ratios of Fibonacci numbers. Fermat's spiral has also been found to be an efficient layout for the mirrors of concentrated solar power plants.〔 〕 __NOTOC__ == See also == * Patterns in nature * Spiral of Theodorus 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「Fermat's spiral」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.