lim(sin)^tanx(x趋近于二分之派)

1个回答

  • 解法一:∵lim(x->π/2)[(sinx-1)tanx]

    =lim(x->π/2){[(sinx-1)/cosx]sinx}

    =lim(x->π/2)[(sinx-1)/cosx]*lim(x->π/2)(sinx)

    =lim(x->π/2){[sin(x/2)-cos(x/2)]/[cos(x/2)+sin(x/2)]}*1

    =0*1

    =0

    lim(x->π/2){(sinx)^[1/(sinx-1)]}

    =lim(x->π/2){(1+sinx-1)^[1/(sinx-1)]}

    =e (应用特殊极限lim(x->0)[(1+x)^(1/x)]=e)

    ∴原式=lim(x->π/2)[(sinx)^tanx]

    =lim(x->π/2)【(sinx)^{[1/(sinx-1)]*[(sinx-1)tanx]}】

    =【lim(x->π/2){(sinx)^[1/(sinx-1)]}】^{lim(x->π/2)[(sinx-1)tanx]}

    =e^{lim(x->π/2)[(sinx-1)tanx]}

    =e^0

    =1.

    解法二:原式=lim(x->π/2)[(sinx)^tanx]

    =lim(x->π/2){e^[tanx*ln(sinx)]}

    =e^{lim(x->π/2)[tanx*ln(sinx)]}

    =e^{lim(x->π/2)[ln(sinx)/cotx]}

    =e^[lim(x->π/2)(-cotx/csc²x)]

    =e^[lim(x->π/2)(-sinx*cosx)]

    =e^0

    =1.