常用等价无穷小:当x→>Q时, sInx x, arcsinx d tanx r, arctan x, In(1+x)x, e-lox, 1-cosxvx 2 im=,…linQ-β =0.即a-β=0(a), 于是有a=β+o(ax) 例如,Sinx=x+0(x) c0Sx=1-。x2+0(x2) 2常用等价无穷小: 当x → 0时, lim = 1,    lim = 0,   -   即 -  = o(), 于是有  =  + o(). 例如, sin x = x + o(x),( ). 2 1 cos 1 2 2 x = - x + o x . 2 1 ln(1 ) ~ , 1 ~ , 1 cos ~ tan ~ , arctan ~ , sin ~ , arcsin ~ , 2 x x e x x x x x x x x x x x x + - -