令u=arctanX,则原式=lim(u趋2/派) tan(u)*(2/派- u)
=lim(u趋2/派) sin(u) * (2/派- u) /cos(u)
=lim(u趋2/派) sin(u) * lim(u趋2/派)(2/派- u) /cos(u)
=1 * lim(u趋2/派) (2/派- u) /cos(u) 【0比0型】
=lim(u趋 2/派) (-1) /[-sin(u) ]【洛比达法则】
=1
令u=arctanX,则原式=lim(u趋2/派) tan(u)*(2/派- u)
=lim(u趋2/派) sin(u) * (2/派- u) /cos(u)
=lim(u趋2/派) sin(u) * lim(u趋2/派)(2/派- u) /cos(u)
=1 * lim(u趋2/派) (2/派- u) /cos(u) 【0比0型】
=lim(u趋 2/派) (-1) /[-sin(u) ]【洛比达法则】
=1