# Tag Info

Let $\psi_\lambda(x, c)$, $\phi_\mu(y, {\tilde c})$ be the eigenfunctions of $H_x(c )$ and $H_y({\tilde c})$ respectively, $$H_x \psi_\lambda(x, c) = \lambda(c) \psi_\lambda(x, c)$$ $$H_y \phi_\mu(y, {\tilde c}) = \mu({\tilde c}) \phi_\mu(y, {\tilde c})$$ Since both $\lbrace \psi_\lambda\rbrace_\lambda$ and $\{\phi_\mu\}_\mu$ must be basis sets, there ...