【正文】
i m0?? 21)21( ?? t 21)1( ??? t2)1()21(l i m2323210????????ttt 41??4. 求 5. 求 ]。)11l n ([lim 2 xxxx ????解 : ? ?tttt1)1l n (1l i m20 ??? ?20)1l n (l i mtttt????)1(2l i m 0 tttt ????ttt 21lim 1 10?? ??1??xt1?令原式 令 ,12xt ? 則 tt et????50lim原式 = tx et 50lim????0???tt et 4950lim????211 0 00 xxex??解 : tt e!50lim????(用洛必達(dá)法則 ) (繼續(xù)用洛必達(dá)法則 ) )co s1(s e c])1l n [ (lim22220 xxxxx ????xxxx 2420 s i n)1(lnlim ????2420limxxxx???xxxxxxx c o ss e c)1l n ()1l n ( 220 ???????解 : 原式 = 1?.)1(lim ??? nn nn 型0??21 l i m???? nn解 )1(l i m121 ????nnnn1ln1 ?nne21lim ????nnnnln121lnlimnnn ???02lim211lim2121??????????xxxxx原式 21lnlimxxx ????8. 求