Trigonometry is the study of the relations between the sides and angles of triangles. The word “trigonometry” is derived from the Greek words trigono (\(\text{τ}\text{ρ}\acute{\text{ι}}\text{γ}\text{ω}\text{ν}\)o), meaning “triangle”, and metro (\(\text{μ}\text{ε}\text{τ}\text{ρ}\acute{\text{ω}}\)), meaning “measure”. Though the ancient Greeks, such as Hipparchus and Ptolemy, used trigonometry in their study of astronomy between roughly 150 b.c. - a.d. 200, its history is much older. For example, the Egyptian scribe Ahmes recorded some rudimentary trigonometric calculations (concerning ratios of sides of pyramids) in the famous Rhind Papyrus sometime around 1650 b.c.[1]
Trigonometry is distinguished from elementary geometry in part by its extensive use of certain functions of angles, known as the trigonometric functions. Before discussing those functions, we will review some basic terminology about angles.
- Ahmes claimed that he copied the papyrus from a work that may date as far back as 3000 b.c. ↩