(1-1/2的2次方)(1-1/3的2次方) (1-1/2010^2)
=(1-1/2)(1+1/2)(1-1/3)(1+1/3)...(1-1/2009)(1+1/2009)(1-1/2010)(1+1/2010)
=1/2*3/2*2/3*4/3*...2009/2010*2011/2010
=2011/4020
(1-1/2的2次方)(1-1/3的2次方) (1-1/2010^2)
=(1-1/2)(1+1/2)(1-1/3)(1+1/3)...(1-1/2009)(1+1/2009)(1-1/2010)(1+1/2010)
=1/2*3/2*2/3*4/3*...2009/2010*2011/2010
=2011/4020