ect to $r$
          evaluated at $r=4$, $\theta=\pi/2$. Plot this vector on
          the graph you drew in the previous part, starting at the
          point you drew.</li>

          <li>Compute $\ds \frac{\partial \vec T}{\partial
          \theta}(4,\pi/2)$, i.e., the partial with respect to
          $\theta$ evaluated at $r=4$, $\theta=\pi/2$. Plot this
          vector on the graph you drew in the previous part,
          starting at the point you drew.</li>
        </ol>
      </li>

      <li>If y