lim(2-x)tanπ/4x

问题描述:

lim(2-x)tanπ/4x

应用罗比达法则
lim(2-x)tanπx/4
=lim(2-x)/cot(πx/4)
=lim(-1/[-πcsc^2(πx/4)/4])
=4limsin^2(πx/4)/π
=4/π