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Zhao Youqin's algorithm was an algorithm by Yuan dynasty astronomer-mathematician Zhao Youqin (, ? – 1330) to calculate the value of in his book ''Ge Xiang Xin Shu'' (). == Algorithm == Zhao Youqin started with an inscribed square in a circle with radius r.〔Yoshio Mikami, Development of Mathematics in China and Japan, Chapter 20, The Studies about the Value of etc., pp 135–138〕 If denotes the length of a side of the square, draw a perpendicular line d from the center of the circle to side l. Let e denotes r − d. Then from the diagram: : : Extend the perpendicular line d to dissect the circle into an octagon; denotes the length of one side of octagon. : : let denotes the length of a side of hexadecagon : similarly : Proceeding in this way, he at last calculated the side of a 16384-gon, multiplying it by 16384 to obtain 3141.592 for a circle with diameter = 1000 units, or : He multiplied this number by 113 and obtained 355. From this he deduced that of the traditional values of , that is 3, 3.14, and , the last is the most exact.〔Yoshio Mikami, p136〕 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「Zhao Youqin's π algorithm」の詳細全文を読む スポンサード リンク
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