BibTeX: 
@article{Cotangent_PFD_FormulaAFP,
author = {Manuel Eberl},
title = {A Proof from THE BOOK: The Partial Fraction Expansion of the Cotangent},
journal = {Archive of Formal Proofs},
month = mar,
year = 2022,
note = {\url{https://isaafp.org/entries/Cotangent_PFD_Formula.html},
Formal proof development},
ISSN = {2150914x},
}
