e can
  compare it with the formal definition of limits in higher
  dimensions. The only difference is that we just put vector
  symbols above the input $x$ and the output $f(x)$.</p>

  <div class="definition">
    Let $\vec f:\RR^n\to\RR^m$ be a function. We write $\ds
    \lim_{\vec x\to \vec c} \vec f(\vec x)=\vec L$ if and only if
    for every $\epsilon&gt;0$, there exists a $\delta&gt;0$ such
    that $0&lt;|\vec x-\vec c|&lt;\delta$ implies $|\vec f(\vec
    x)-\vec L|&lt;\epsilon$.
  </div>
       