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\begin{frame}
  \frametitle{The Substitution Rule: Exercises}
  
  
  \begin{exampleblock}{}
    Evaluate
    \begin{talign}
      \int_0^1 \cos(\pi x/2)\, dx 
    \end{talign}
    \pause
    
    We take $u = \pause \pi x/2$\pause, then $u' = \pause \pi/2$ \pause and
    \begin{talign}
      \int_0^1 \cos(\pi x/2)\, dx 
      \mpause[1]{ &= \int_{u(0)}^{u(1)} \cos(u) \, \frac{du}{\pi/2} }\\
      \mpause{ &= \frac{2}{\pi}\int_{0}^{\pi/2} \cos(u) \, du }\\
      \mpause{ &= \frac{2}{\pi} \left( \sin u\big]_{0}^{\pi/2} \right) }\\
      \mpause{ &= \frac{2}{\pi} \left(\sin(\pi/2) - \sin(0) \right)}\\
      \mpause{ &= \frac{2}{\pi} }
    \end{talign}\vspace{-1.5ex}
    \pause\pause\pause\pause%
  \end{exampleblock}
\end{frame}