trigonometric identities - SERP Analysis

https://en.wikipedia.org/wiki/List_of_trigonometric_identities

https://www.mvcc.edu/learning-commons/pdf/trigonometric-identities-sept-2017.pdf

https://www.youtube.com/watch%3Fv%3Dm1OitPmkydY

https://www.purplemath.com/modules/idents.htm

https://byjus.com/maths/trigonometric-identities/

https://tutorial.math.lamar.edu/pdf/trig_cheat_sheet.pdf

https://mathcs.clarku.edu/~djoyce/trig/identities.html

https://www.khanacademy.org/math/trigonometry/trig-equations-and-identities

https://www.mga.edu/computing/mathematics-statistics/docs/Math_Resources_Trigonometric_Formulas.pdf