lim(x→0)tan4X/sin3X

问题描述:

lim(x→0)tan4X/sin3X

lim(x→0)sin4x/sin3x cos4x
=lim(x→0) sin4x/4x ×3x/sin3x ×1/cos4x ×4/3
=1×1×1×4/3
=4/3为什么要加上cos4X呢tan4x=sin4x/cos4x当x趋近于0时sin4x/4x=1sin3x/3x=1cos4x=1