[Tex/LaTex] Making equation fit on one beamer slide

beamerequationsfontsize

I'm doing a presentation and one of the slides has a particularly long equation, which I want to fit on the page. What's the best way to fit this on the page without altering the size of the other text slides? Thanks in advance.

\documentclass{beamer}
\usetheme{metropolis}
\begin{document}
\begin{frame}
\frametitle{Equation}
\begin{align}\label{global_energy_slab_sl_1}
    &|\mathcal{\hat R}|^2+|\mathcal{\hat T}|^2 = \frac{1+|\hat V|^2}{|\hat H|^2} \\ \nonumber
    &= \frac{1+(r_{0}^{+}r_{1}^{-}e^{i\lambda_{1}^{-}L}+r_{0}^{-}r_{1}^{+}e^{i\lambda_{1}^{+}L})(r_{0}^{+}r_{1}^{-}e^{-i\lambda_{1}^{-}L}+r_{0}^{-}r_{1}^{+}e^{-i\lambda_{1}^{+}L})}{(r_{0}^{-}r_{1}^{-}e^{i\lambda_{1}^{-}L}+r_{0}^{+}r_{1}^{+}e^{i\lambda_{1}^{+}L})(r_{0}^{-}r_{1}^{-}e^{-i\lambda_{1}^{-}L}+r_{0}^{+}r_{1}^{+}e^{-i\lambda_{1}^{+}L})} \\ \nonumber
    &=\frac{1+(r_{0}^{+})^2(r_{1}^{-})^2+(r_{0}^{-})^2(r_{1}^{+})^2+(r_{0}^{-}r_{0}^{+})(r_{1}^{-}r_{1}^{+})e^{2i\zeta_1 L}+(r_{0}^{-}r_{0}^{+})(r_{1}^{-}r_{1}^{+})e^{-2i\zeta_{1} L}}{(r_{0}^{-})^2(r_{1}^{-})^2+(r_{0}^{+})^2(r_{1}^{+})^2+(r_{0}^{-}r_{0}^{+})(r_{1}^{-}r_{1}^{+})e^{2i\zeta_1 L}+(r_{0}^{-}r_{0}^{+})(r_{1}^{-}r_{1}^{+})e^{-2i\zeta_{1} L}},
\end{align}
\end{frame}
\end{document}

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Best Answer

I would simply use, for the longest fractions, the medium-size fractions from nccmath (they're about 80 % of \displaystyle size):

\documentclass{beamer}
\usetheme{metropolis}
\usepackage{nccmath}
\begin{document}

\begin{frame}
\frametitle{Equation}
\begin{align}\label{global_energy_slab_sl_1}
    &|\mathcal{\hat R}|^2+|\mathcal{\hat T}|^2 = \frac{1+|\hat V|^2}{|\hat H|^2} \\ \nonumber
    &= \mfrac{1+(r_{0}^{+}r_{1}^{-}e^{i\lambda_{1}^{-}L}+r_{0}^{-}r_{1}^{+}e^{i\lambda_{1}^{+}L})(r_{0}^{+}r_{1}^{-}e^{-i\lambda_{1}^{-}L}+r_{0}^{-}r_{1}^{+}e^{-i\lambda_{1}^{+}L})}{(r_{0}^{-}r_{1}^{-}e^{i\lambda_{1}^{-}L}+r_{0}^{+}r_{1}^{+}e^{i\lambda_{1}^{+}L})(r_{0}^{-}r_{1}^{-}e^{-i\lambda_{1}^{-}L}+r_{0}^{+}r_{1}^{+}e^{-i\lambda_{1}^{+}L})} \\[1ex] \nonumber
   & =\mfrac{1+(r_{0}^{+})^2(r_{1}^{-})^2+(r_{0}^{-})^2(r_{1}^{+})^2+(r_{0}^{-}r_{0}^{+})(r_{1}^{-}r_{1}^{+})e^{2i\zeta_1 L}+(r_{0}^{-}r_{0}^{+})(r_{1}^{-}r_{1}^{+})e^{-2i\zeta_{1} L}}{(r_{0}^{-})^2(r_{1}^{-})^2+(r_{0}^{+})^2(r_{1}^{+})^2+(r_{0}^{-}r_{0}^{+})(r_{1}^{-}r_{1}^{+})e^{2i\zeta_1 L}+(r_{0}^{-}r_{0}^{+})(r_{1}^{-}r_{1}^{+})e^{-2i\zeta_{1} L}}
\end{align}
\end{frame}

\end{document} 

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