Question

x趋向于0 (tan3x-tanx)/x

Answer 1

lim[x-->0](tan3x-tanx)/x

=lim[x-->0]tan3x/x-lim[x-->0]tanx/x

=lim[x-->0]sin3x/(xcos3x)-lim[x-->0]sinx/(xcosx)

=3-1

=2