利用因式分解计算
(1-1/2^2)(1-1/3^2)(1-1/4^2)(1-1/5^2)……(1-100^2)...
(1-1/2^2)(1-1/3^2)(1-1/4^2)(1-1/5^2)……(1-100^2)
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(1-1/2^2)(1-1/3^2)(1-1/4^2)(1-1/5^2)……(1-100^2)
=(1+1/2)(1-1/2)(1+1/3)(1-1/3)(1+1/4)(1-1/4)(1+1/5)(1-1/5)……(1+1/100)(1-1/100)
=(3/2)(1/2)(4/3)(2/3)(5/4)(3/4)(6/5)(4/5)……(101/100)(99/100)
=(3/2)(4/3)(5/4)(6/5)……(101/100)*(1/2)(2/3)(3/4)(4/5)……(99/100)
=101/2*1/100
=101/200
=(1+1/2)(1-1/2)(1+1/3)(1-1/3)(1+1/4)(1-1/4)(1+1/5)(1-1/5)……(1+1/100)(1-1/100)
=(3/2)(1/2)(4/3)(2/3)(5/4)(3/4)(6/5)(4/5)……(101/100)(99/100)
=(3/2)(4/3)(5/4)(6/5)……(101/100)*(1/2)(2/3)(3/4)(4/5)……(99/100)
=101/2*1/100
=101/200
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