(1+1/2)*(1-1/2)*(1+1/3)*(1-1/3)........*(1+1/99)*(1-1/99)=( )
(1+1/2)*(1-1/2)*(1+1/3)*(1-1/3)........*(1+1/99)*(1-1/99)=( )
(1+1/2)*(1-1/2)*(1+1/3)*(1-1/3)........*(1+1/99)*(1-1/99)
=[1-(1/2)*(1/2)][1-(1/3)*(1/3)].......*[1-(1/99)*(1/99)]
=[3/(2*2)]*[8/(3*3)].......*[9800/(99*99)]
=[3/(2*2)]*[(2*4)/(3*3)]*[(3*5)/(4*4)]*[(4*6)/(5*5)].......*[(98*100)/(99*99)] 约分
=(1/2)*(100/99)
=50/99