計算(1+1/2)*(1-1/3)*(1+1/4)*(1-1/5)*.*(1+1/1000)*(1-1/1001)

計算(1+1/2)*(1-1/3)*(1+1/4)*(1-1/5)*.*(1+1/1000)*(1-1/1001)

(1+1/2)*(1-1/3)*(1+1/4)*(1-1/5)*.*(1+1/1000)*(1-1/1001)
=3/2*2/3*5/4*4/5*……*1001/1000*1000/1001
=1*1*1*……*1*1
=1