
   $$
      \lim_{x\to0}\frac{\sin^4 x \cos x}{x^4}         =
      {\left(\lim_{x\to0}\frac{\sin x}x\right)}^4 \cdot
      \lim_{x \to 0} \cos x = 1^4 \cdot 1             = 1.
   $$
