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In mathematics, the arithmetic–geometric mean (AGM) of two positive real numbers and is defined as follows: First compute the arithmetic mean of and and call it . Next compute the geometric mean of and and call it ; this is the square root of the product : : Then iterate this operation with taking the place of and taking the place of . In this way, two sequences and are defined: : These two sequences converge to the same number, which is the arithmetic–geometric mean of and ; it is denoted by , or sometimes by . This can be used for algorithmic purposes as in the AGM method. ==Example== To find the arithmetic–geometric mean of and , first calculate their arithmetic mean and geometric mean, thus: : and then iterate as follows: : The first five iterations give the following values: : As can be seen, the number of digits in agreement (underlined) approximately doubles with each iteration. The arithmetic–geometric mean of 24 and 6 is the common limit of these two sequences, which is approximately 13.4581714817256154207668131569743992430538388544.〔(agm(24, 6) at WolframAlpha )〕 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「Arithmetic–geometric mean」の詳細全文を読む スポンサード リンク
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