(1-1/2²)(1-1/3²)(1-1/4²)……(1-1/9²)(1-1/10²)简便方法,
问题描述：
(1-1/2²)(1-1/3²)(1-1/4²)……(1-1/9²)(1-1/10²)简便方法,
答
用平方差
=(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)
中间约分
=(1/2)(11/10)
=11/20