坐标转换A（3cos(π/4),3sin(π/4)）,B（-3cos(π/12),-3sin(π/12)）
|AB|=√((3cos(π/4)+3cos(π/12))²+（3sin(π/4)+3sin(π/12))²)
=3√(2+2cos(π/4-π/12))
=3√(2+√3)