l formulas.
        </div>
          Show that we can write $dV$ as the matrix product
        of a 1-row by 2-column matrix with a 2-row by 1-column
        matrix: $$dV = \begin{bmatrix}2\pi rh&amp; \pi
        r^2\end{bmatrix}\begin{bmatrix}dr\\dh\end{bmatrix}.$$ How
        do the columns of the first matrix relate to the
        calculations you did above?

        <p>The matrix $\begin{bmatrix}2\pi rh&amp; \pi
          r^2\end{bmatrix}$ is the <em>derivative</em> of $V$. The columns
          of this