先用罗比达法则对分子分母分别求导,得：cost的立方*根号下tan(sint)/根号下sin(tant),当x-0时,cost=1,再对上式用等价无穷小替换得：根号下sint/根号下tant,等于1
lim(x— 0)根号tanx在0到sint的无穷积分/根号sinx在0到tant的无穷积分
先用罗比达法则对分子分母分别求导,得：cost的立方*根号下tan(sint)/根号下sin(tant),当x-0时,cost=1,再对上式用等价无穷小替换得：根号下sint/根号下tant,等于1