1减二的平方分之一乘1减三的平方之一一直到2011 =（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+1/2)(1+1/3)(1+1/4)……(1+1/2011)(1-1/2)(1-1/3)(1-1/4)……(1-1/2011）=3/2*4/3*5/4*…...