数列极限题目.求lim(cosa^n+sina^n)/(cos^n-sina^n)(0

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数列极限题目.求lim(cosa^n+sina^n)/(cos^n-sina^n)(0数列极限题目.求lim(cosa^n+sina^n)/(cos^n-sina^n)(0数列极限题目.求lim(co

数列极限题目.求lim(cosa^n+sina^n)/(cos^n-sina^n)(0
数列极限题目.
求lim(cosa^n+sina^n)/(cos^n-sina^n)(0

数列极限题目.求lim(cosa^n+sina^n)/(cos^n-sina^n)(0
分子分母同时处以cosa^n,然后分情况讨论,当a在0到π/4的时候,tana^n等于0,那么原式=1;当a在π/4到π/2时,原式不像原来那样除以cosa^n,而是除以sina^n,当a在π/4到π/2时,tana^n趋向于无穷大,则其倒数趋向于0,原式=-1.
故当a在0到π/4的时,等于1
当a在π/4到π/2时,等于-1

0sina>0;
lim(cosa^n+sina^n)/(cos^n-sina^n)=1
派/4cosa>0;
lim(cosa^n+sina^n)/(cos^n-sina^n)=-1

楼主题目的含义不清楚:
n次方是角度的n次方?还是三角函数的n次方?