f(x)={sinx+1 x≥0,2x-1 x
问题描述：
f(x)={sinx+1 x≥0,2x-1 x
答
就是求f(x)的左右极限,
lim(x→0+)f(x)
= sin0 +1
= 1
而
lim(x→0-)f(x)
= 2*0 -1
= -1