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问题: 数学

计算:(1-1/2^2)(1-1/3^2)(1-1/4^2)…………(1-1/2007^2)(1-1/2008^2)

解答:

计算:(1-1/2^2)(1-1/3^2)(1-1/4^2)…………(1-1/2007^2)(1-1/2008^2)

原式=
(1-1/2)(1+1/2)(1-1/3)(1+1/3)(1-1/4)(1+1/4)……(1-1/2006)(1+1/2006)(1-1/2007)(1+1/2007)(1-1/2008)(1+1/2008)
=(1/2)(3/2)(2/3)(4/3)(3/4)(5/4)……(2005/2006)(2007/2006)(2006/2007)(2008/2007)(2007/2008)(2009/2008)
=(1/2)[(3/2)(2/3)][(4/3)(3/4)](5/4)……(2005/2006)[(2007/2006)(2006/2007)][(2008/2007)(2007/2008)](2009/2008)
=(1/2)*1*1*……*1*1*(2009/2008)
=2009/4016