The author delves into the controversial topic of different definitions for sine and cosine in math, arguing that starting from intuitive geometric definitions would make more sense than utilizing complex series or differential equations. The article provides a clear and unambiguous geometric proof of the angle addition formulas, emphasizing the importance of grounding mathematical concepts in basic principles. The author challenges the traditional approach of defining sine and cosine, advocating for a more pedagogically sound foundation. Through insightful explanations and detailed proofs, the article aims to offer a refreshing perspective on the origins and derivations of trigonometric functions.
https://www.oranlooney.com/post/angle-addition/