当x→0x \to 0x→0时,1−cosx1-\cos x1−cosx是ln(1+12x2)\ln(1 + \dfrac{1}{2}x^{2})ln(1+21x2)的( ).
(A)高阶无穷小
(B)低阶无穷小
(C)等价无穷小
(D)同阶但非等价无穷小
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