x趨近於0時,lim(x-sin(3x))/(x+sinx)

x趨近於0時,lim(x-sin(3x))/(x+sinx)

lim(x→0)(x-sin(3x))/(x+sinx)(這是0/0型,運用洛必達法則)
=lim(x→0)(1-3cos3x)/(1+cosx)
=-1