解:(1-1/2²)(1-1/3²)(1-1/4²)...(1-1/10²)
=[(1+1/2)(1-1/2)]*[(1+1/3)(1-1/3)]*[(1+1/4)(1-1/4)]...[(1+1/10)(1-1/10)]
=(3/2)*(1/2)*(4/3)*(2/3)*(5/4)*(3/4)...(11/10)*(9/10){注意3/2与2/3乘积1,4/3与3/4乘积1...一次类推,结果只有第一项的1/2和最后项的11/10没人配为1哦,呵呵!}
=(1/2)*(11/10)
=11/20
(如果还是看不懂再密我哦)
用平方差
原式=(1-1/2)(1+1/2)(1-1/3)(1+1/3)……(1-1/10)(1+1/10)
=(1/2)(3/2)(2/3)(4/3)……(9/10)(11/10)
=(1/2)(11/10)
=11/20