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求(sin2/x+cos1/x)^x的极限,当x趋向于无穷

题目详情
求(sin2/x+cos1/x)^x的极限,当x趋向于无穷
▼优质解答
答案和解析
  记 t=1/x,
  先计算
   lim(t→0)ln(sin2t+cost)/t (0/0)
  = lim(t→0)(2cos2t-sint)/(sin2t+cost)
  = 2,  

   lim(x→∞)[sin(2/x)+cos(1/x)]^x
  = lim(t→0)(sin2t+cost)^(1/t)
  = e^lim(t→0)ln(sin2t+cost)/t
  = e^2.