（1-½²）（1-⅓²）（1-¼²）……（1-1／100²）=(1-1/2)(1+1/2)(1-1/3)(1+1/3)(1-1/4)(1+1/4)...(1-1/100)(1+1/100)=1/2x3/2x2/3x4/3x3/4x5/4.x99/100x101/100=1/2x1x1.x1x101/100...