此题最简单的求解方法是“罗布达法则”法!解法如下.
∵lim(x->1)[(1-x)/cos(πx/2)]=lim(x->1){(-1)/[(-π/2)sin(πx/2)]} (0/0型极限,应用罗比达法则)
=(2/π)lim(x->1)[1/sin(πx/2)]
=2/π
∴lim(x->1)[(1-x)tan(πx/2)]=lim(x->1)[(1-x)sin(πx/2)/cos(πx/2)]
=lim(x->1)sin(πx/2)*lim(x->1)[(1-x)/cos(πx/2)]
=1*(2/π)
=2/π.