求(1-1/2^2)(1-1/3^2)(1-1/4^2)(1-1/5^2)…(1-1/2012^2)的值
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(1-1/2^2)(1-1/3^2)(1-1/4^2)(1-1/5^2)…(1-1/2012^2)
=(1-1/2)(1+1/2)(1-1/3)(1+1/3)(1-1/4)(1+1/4)...(1-1/2011)(1+1/2011)(1-1/2012)(1+1/2012)
=[(1/2)(2/3)(3/4)...(2010/2011)(2011/2012)]×[(3/2)(4/3)(5/4)...(2012/2011)(2013/2012)]
=(1/2012)×(2013/2)
=2013/4024
=(1-1/2)(1+1/2)(1-1/3)(1+1/3)(1-1/4)(1+1/4)...(1-1/2011)(1+1/2011)(1-1/2012)(1+1/2012)
=[(1/2)(2/3)(3/4)...(2010/2011)(2011/2012)]×[(3/2)(4/3)(5/4)...(2012/2011)(2013/2012)]
=(1/2012)×(2013/2)
=2013/4024
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