找高人求极限

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找高人求极限
找高人求极限

找高人求极限
(1)原式=lim(x->∞)[(e^(1/x)-1)/(1/x)]
=lim(x->∞)[(1/x)/(1/x)] (等价代换:当x->∞时,e^(1/x)~1/x)
=lim(x->∞)(1)
=1;
(2)原式=lim(n->∞){[2^n*cos(x/2)cos(x/2²).cos(x/2^n)sin(x/2^n)]/[2^n*sin(x/2^n)]}
(分子分母同乘2^n*sin(x/2^n))
=lim(n->∞){[sinx/[2^n*sin(x/2^n)]}
=(sinx/x)*lim(n->∞)[(x/2^n)/sin(x/2^n)] (∵x≠0)
=(sinx/x)*1 (应用重要极限lim(z->0)(sinz/z)=1)
=sinx/x.