祖冲之和圆周率

　　月球背面有一座环形山，被命名为“祖冲之环形山”。

　　祖冲之(公元429-500年)是中国南北朝时著名的数学家、天文学家和机械制造家。他从小聪明好学，爱好自然科学、文学和哲学，经过刻苦的学习钻研，终于成为一位享誉世界的科学家。

　　祖冲之在数学方面的成就为世界所公认。远在1,500多年前，祖冲之就计算出了精确的圆周率a。圆周率通常用“π”来表示，求算圆周率的值是数学中一个非常重要也是非常困难的研究课题。中国古代许多数学家都为研究这个课题付出了心血，并取得了喜人的成果。祖冲之在前人研究的基础上，继续进行了深入系统的研究，经过1,000多次的计算，得出圆周率在3.1415926和3.1415927之间，成为世界上第一个把圆周率推算到小数点后七位数字的科学家。祖冲之还提出π的近似值为355/113，称为“密率”，把数学中关于圆周率的计算推进到一个新阶段，成为当时世界上最精确的圆周率。日本数学家尊称它为“祖率”。直到1,000多年以后，西方的数学家才达到和超过了祖冲之的成就。

　　Zu Chongzhi (429-500 AD) was a famous mathematician, astronomer and mechanic in the Southern and Northern dynasties (421-581 AD). Smart and fond of learning since childhood, he liked natural science, literature and philosophy, and later became a world-famous scientist.

　　The achievements Zu Chongzhi made in mathematics have been universally acknowledged. He worked out an accurate value of pia. Pi is usually represented by , and it has always been a very important yet difficult research topic for mathematics to calculate the value of pi. Many mathematicians of ancient China made painstaking efforts in this research with satisfactory results. Based on earlier research, Zu Chongzhi continued to carry out systematic study. After calculating more than 1,000 times, he concluded that the value of pi falls between 3.1415926 and 3.1415927; and therefore he became the first scientist in the world who calculated the value of pi to seven decimal places. Zu Chongzhi also put forward the thesis that the approximate value of pi was 355/113, which was called milv(close ratio), pushing the calculation of pi to a new stage. The value was the most accurate in the world at that time, and Japanese scientists respectfully called it the "zu Chongzhi Ratio". Not until more than 1,000 years later, did scientists in the West come up to and surpass the achievements of Zu Chongzhi.