证明:对任意ε>0,解不等式
│(1+cos(π/(2(n+1))))/n-0│≤(1+│cos(π/(2(n+1)))│)/n≤2/n2/ε,取N≥[2/ε].
于是,对任意ε>0,总存在N≥[2/ε],当n>N时,有│(1+cos(π/(2(n+1))))/n-0│∞)[(1+cos(π/(2(n+1))))/n]=0.
证明:对任意ε>0,解不等式
│(1+cos(π/(2(n+1))))/n-0│≤(1+│cos(π/(2(n+1)))│)/n≤2/n2/ε,取N≥[2/ε].
于是,对任意ε>0,总存在N≥[2/ε],当n>N时,有│(1+cos(π/(2(n+1))))/n-0│∞)[(1+cos(π/(2(n+1))))/n]=0.