math 10 Secret Trig Functions Your Math Teachers Never Taught You David Ellis Read more posts by this author. David Ellis 2 Dec 2020 • 1 min read 10 Secret Trig Functions Your Math Teachers Never Taught YouHaversine? Exsecant? An introduction to obsolete trig functions and why we don’t use them anymoreEvelyn LambScientific American Blog NetworkExcerpt from https://blogs.scientificamerican.com/roots-of-unity/10-secret-trig-functions-your-math-teachers-never-taught-you/