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π是一个无理数,所以不能直接表示出来。
圆周率(π):3.14159 26535 89793 23846 2643383279 50288 41971 69399 37510 58209 74944 59230 78164 06286 20899 86280 34825 34211 70679 82148 08651 32823 06647 09384 46095 50582 23172 53594 08128 48111 74502 84102 70193 85211.........(约等于3.141592654),通常用3.14来表示π的数值。
一般用希腊字母π表示,是一个在数学及物理学中普遍存在的数学常数。π也等于圆形之面积与半径平方之比。是精确计算圆周长、圆面积、球体积等几何形状的关键值。 在分析学里,π可以严格地定义为满足sin x = 0的最小正实数x。

扩展资料:
以圆形半径为边长作一正方形,然後把圆形面积和此正方形面积的比例定为
,即圆形之面积与半径平方之比。定义圆周率不一定要用到几何概念,比如,我们可以定义
为满足
的最小正实数
。
这里的正弦函数定义为幂级数
π是个无理数,即不可表达成两个整数之比,是由瑞士科学家约翰·海因里希·兰伯特于1761年证明的。 1882年,林德曼更证明了π是超越数,即π不可能是任何整系数多项式的根。
圆周率的超越性否定了化圆为方这古老尺规作图问题的可能性,因所有尺规作图只能得出代数数,而超越数不是代数数。
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