求极限lim(x→∞)(sin1/x-cos1/x)^x

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求极限lim(x→∞)(sin1/x-cos1/x)^x

求极限lim(x→∞)(sin1/x-cos1/x)^x
求极限lim(x→∞)(sin1/x-cos1/x)^x

求极限lim(x→∞)(sin1/x-cos1/x)^x
x→∞
1/x→0
cos1/x→1
sin1/x~1/x
lim(x→∞)(sin1/x-cos1/x)^x
=lim(x→∞)(1/x-1)^x
=-lim(x→∞)(1-1/x)^x
=-lim(x→∞)(1+(-1/x)^(-x)*(-1)
=-e^(-1)
=-1/e

应该是
lim(x→∞)[cos(1/x)-sin(1/x)]^x。
先计算
lim(x→∞)x*ln|cos(1/x)-sin(1/x)|
= lim(t→0)ln|cost-sint|/t (0/0) (令 t=1/x)
= lim(t→0)(-sint-cost)/(cost-sint...

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应该是
lim(x→∞)[cos(1/x)-sin(1/x)]^x。
先计算
lim(x→∞)x*ln|cos(1/x)-sin(1/x)|
= lim(t→0)ln|cost-sint|/t (0/0) (令 t=1/x)
= lim(t→0)(-sint-cost)/(cost-sint)
= -1,

lim(x→∞)(sin1/x-cos1/x)^x = e^(-1)。

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