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求以下两个,当x趋于0时的极限,

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求以下两个,当x趋于0时的极限,
求以下两个,当x

趋于0时的极限,

求以下两个,当x趋于0时的极限,
lim(x→0)[√(1+sinx)-1] = lim(x→0)[(1/2)sinx] = 0;
 lim(x→0)[√(1+tanx)-√(1+sinx)]/(x^k)
  = lim(x→0)√(1+sinx)]*lim(x→0){√[(1+tanx)/(1+sinx)]-1}/(x^k)
  = 1*lim(x→0){√[1+(tanx-sinx)/(1+sinx)]-1}/(x^k)
  = 1*lim(x→0){(1/2)[(tanx-sinx)/(1+sinx)]}/(x^k) (等价无穷小替换)
  = (1/2)*lim(x→0)[1/(1+sinx)]*lim(x→0)[(tanx-sinx)/(x^k)]
  = (1/2)*1*lim(x→0)[(tanx-sinx)/(x^k)]
  = (1/2)*lim(x→0)(1/cosx)*lim(x→0)(sinx/x)*lim(x→0){(1-cosx)/[x^(k-1)]}
  = (1/2)*1*1*(1/2) = 1/4,k=3,
  = 0,k3.