\begin{frame}
  \frametitle{The Substitution Rule: Exercises}
  
  \begin{exampleblock}{}
    Evaluate
    \begin{talign}
      \int x \sin(x^2)\, dx 
    \end{talign}
    \pause
    We take $u = \pause x^2$\pause, then $u' = \pause 2x$ \pause and
    \begin{talign}
      \int x \sin(x^2)\, dx 
      \mpause[1]{ &= \int x\sin u \, \frac{du}{2x} } \\
      \mpause{ &= \frac{1}{2} \int \sin u \, du }\\
      \mpause{ &= -\frac{1}{2}\cos u + C }\\
      \mpause{ &= -\frac{1}{2}\cos x^2 + C }
    \end{talign}
    \pause\pause\pause
  \end{exampleblock}
\end{frame}