$ \displaystyle\lim_{x \to 0} \frac{1-cos^3 x}{x \cdot tanx} = $
$ = \displaystyle\lim_{x \to 0} \frac{(1-cos x)(1+cosx+cos^2 x)}{x^2 \cdot \frac{tanx}{x}} = $
$ = \displaystyle\lim_{x \to 0} \frac{(1-cos x)}{x^2} \cdot \frac{(1+cosx+cos^2 x)}{\frac{tanx}{x}} = \frac{1}{2} \cdot \frac{3}{1} = \frac{3}{2}$