有没有好办法？

来源: 于 2012-01-13 09:00:51 [旧帖] [给我悄悄话] 本文已被阅读：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.