你好！当x→-∞，arctanx→-π/2，原式=(-π/2)/(-∞)=0当x→+∞,arctanx→π/2，原式=(π/2)/(+∞)=0所以原式=0事实上，-π/2<arctanx<π/2，是有界的而分母x是无穷，有界/无穷=0

1.当x→-∞，arctanx→-π/2，原式=(-π/2)/(-∞)=0

2.当x→+∞,arctanx→π/2，原式=(π/2)/(+∞)=0

3.所以原式=0

4.事实上，-π/2