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diff --git a/doc/Eqs/dihedral_multi_harmonic.tex b/doc/Eqs/dihedral_multi_harmonic.tex
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+\documentclass[12pt]{article}
+
+\begin{document}
+
+$$  
+  E = \sum_{n=1,5} A_n  \cos^{n-1}(\phi)
+$$
+
+\end{document}
\ No newline at end of file