) = \frac{\sin(x)}{2x^2+3}$ and $g(x)=\sqrt{x^2+1}$. Notice
    we don't know $f(x)$.

    <div class="marginpar">
      Not knowing a function $f$ is actually quite common in real
      life. We can often measure how something changes (a
      derivative) without knowing the function itself.
    </div>

    <ol>
      <li>State $f'(x)$ and $g'(x)$.</li>

      <li>State $f'(g(x))$, and explain the difference between
      $f'(x)$ and $f'(g(x))$.</li>

      <li>Use the chain rule to compute $(f\circ g)'(x)