有沒有好辦法？

來源: 於 2012-01-13 09:00:51 [舊帖] [給我悄悄話] 本文已被閱讀：次

Three points A,B,C are chosen at random on a circle. The probability that there exists a point P inside an equilateral triangle A_1B_1C_1 such that PA_1=BC,PB_1=AC,PC_1=AB can be expressed in the form \frac{m} {n}, where m,n are relatively prime positive integers. Find m+n.