derivative is a column. Use Sage to check your
        answer (see the link to Sage in the margin of
        <a href="#derivative-practice">this problem</a> for help
        with how to do this)]
      </li>

      <li>Consider the polar point $(r,\theta) = (4,\pi/2)$:

        <ol>
          <li>Compute $T(4,\pi/2)$ (i.e., the $x,y$ coordinates for
          the polar point). Draw the point.</li>

          <li>Compute $\ds \frac{\partial \vec T}{\partial
          r}(4,\pi/2)$, i.e., the partial with resp