(1-1/2^2)(1-1/3^2)……(1-1/2008^2) =(1-1/2)(1+1/2)(1-1/3)(1+1/3)……(1-1/2008)(1+1/2008) =(1/2)(3/2)(2/3)(4/3)……(2007/2008)(2009/2008) 中间约分约掉了 =(1/2)(2009/2008) =2009/4016
