# A Simple Geometric Proof of the Addition Formula for the Sine

by Jeffrey Li-chieh Ho (Scottsboro High School, AL)

College Mathematics Journal
May, 1994

Subject classification(s): Geometry and Topology | Trigonometry
Applicable Course(s): 2.2 Trigonometry

The following is a short, simple, but not well-known proof of the well-known trigonometric identify $\sin(a+b) = \sin a \cos b + \cos a \sin b$.

A pdf copy of the article can be viewed by clicking below. Since the copy is a faithful reproduction of the actual journal pages, the article may not begin at the top of the first page.