A proof tree for the statement “\(b^* \matches bb\)”:
\[
\begin{prooftree}
\AxiomC{}
\LeftLabel{$\rlnm{Char}$}
\UnaryInfC{$b \matches b$}
\AxiomC{}
\LeftLabel{$\rlnm{Char}$}
\UnaryInfC{$b \matches b$}
\AxiomC{}
\LeftLabel{$\rlnm{StarB}$}
\UnaryInfC{$b^* \matches \epsilon$}
\LeftLabel{$\rlnm{StarS}$}
\BinaryInfC{$b^* \matches b$}
\LeftLabel{$\rlnm{StarS}$}
\BinaryInfC{$b^* \matches bb$}
\end{prooftree}
\]