English

Gold ratio and a trigonometric identity

History and Overview 2009-09-29 v1

Abstract

We give two proofs of the identity cos2π5cosπ5+cosπ5cos2π5=5,\sqrt{\frac{\cos\frac{2\pi}{5}} {\cos\frac{\pi}{5}}}+\sqrt{\frac{\cos\frac{\pi}{5}} {\cos\frac{2\pi}{5}} }=\sqrt{5}, using and not using the gold ratio.

Cite

@article{arxiv.0909.5072,
  title  = {Gold ratio and a trigonometric identity},
  author = {Vladimir Shevelev},
  journal= {arXiv preprint arXiv:0909.5072},
  year   = {2009}
}

Comments

3 pages

R2 v1 2026-06-21T13:51:23.099Z