圓周率則不同，此數本身特殊，確不能以尺規作圖求得，但也可精确表示。

来源: 于 2023-01-13 10:39:42 [旧帖] [给我悄悄话] 本文已被阅读：次

It takes an "infinite series" to define it:

pi / 4  = 1 - 1/3 + 1/5 - 1/7 ..... ( to infinity, but the pattern is clear, unlike the unpredictable  3.1415926.... )

There are many more similar series to define pi, this is the neatest.