lim(1+x)^cot2x (x趋于0)不用洛贝达

2024-11-25 01:47:14
推荐回答(2个)
回答1:

解:∵lim(x->0)[ln(1+x)/sin(2x)]
=lim(x->0)[(1/2)*((2x)/sin(2x))*(ln(1+x)/x)]
=(1/2)*lim(x->0)[(2x)/sin(2x)]*lim(x->0)[ln(1+x)/x]
=(1/2)*1*1 (应用重要极限:lim(z->0)(sinz/z)=1,lim(z->0)(ln(1+z)/z)=1)
=1/2
∴lim(x->0)[(1+x)^(cot(2x))]
=e^{lim(x->0)[cot(2x)*ln(1+x)]} (应用初等函数的连续性)
=e^{lim(x->0)[cos(2x)*(ln(1+x)/sin(2x))]}
=e^{lim(x->0)[cos(2x)]*lim(x->0)[ln(1+x)/sin(2x)]}
=e^[1*(1/2)]
=e^(1/2)
=√e。

回答2:

=limx→0(1+x)^1/tan2x=1^0=1.