企源知识库

设f(x)=
{1-cos2xx＞0
{2x²x≤0
求f′(0)．
【正确答案】：f′-(0)=lim_x→0-[f(x)-f(0)]/(x-0)=lim_x→0-2x²/x=0 f′+(0)=lim_x→0+[f(x)-f(0)]/(x-0)=lim_x→0+