limx->0【1/x】tanx
=lim e^(tanx ln1/x)
=lim e^(x ln1/x)
=lim e^（ln1/x / 1/x）用洛必达
=lim e^(x*(-1/x^2) / (-1/x^2))
=lim e^x
=e^0
=1