(1-二的²分之1）(1-三的²分之1）···（1-2010²分之1）（1-2011²分之一）
=(1+1/2)(1-1/2)(1+1/3)(1-1/3).(1+1/2010)(1-1/2010)(1+1/2011)(1-1/2011)
=(1+1/2)(1+1/3).(1+1/2010)(1+1/2011)(1-1/2)(1-1/3).(1-1/2010)(1-1/2011)
=(3/2)(4/3)...(2011/2010)(2012/2011)(1/2)(2/3)...(2009/2010)(2010/2011)
=(2012/2)(1/2011)
=1006/2011