(1-1/2^2)*(1-1/3^2)*(1-1/4^2)*.*(1-1/2011^2)*(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*3/2*2/3*4/3*3/4*5/4*.*2010/2011*2012/2011*2011/2012*2013/2012
=1/2*2013/2012
=2013/4024
(1-1/2^2)*(1-1/3^2)*(1-1/4^2)*.*(1-1/2011^2)*(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*3/2*2/3*4/3*3/4*5/4*.*2010/2011*2012/2011*2011/2012*2013/2012
=1/2*2013/2012
=2013/4024