(1-1/2^2)(1-1/3^2)(1-1/4^2)···(1-1/n^2)···(1-1/100^2)=(i=2,100)∏(1-1/i^2)=(i=2,100)∏[(1+1/i)(1-1/i)]=(i=2,100)∏(1+1/i)×(i=2,100)∏(1-1/i)=[(3/2)×(4/3)×(5/4)×···×(101/100)]×[(1/2)×(2...