6.5.1 Introduction

Trigonometry, according to its origin in the Greek words trigonon for "triangle" and metron for "measure", is the measuring theory of (angles and sides of) triangles. In this theory, the trigonometric functions sine function, cosine function and tangent function, play a central role.
However, the field of applications of sine, cosine, tangent etc is not restricted to "simple" triangle calculations. In fact, the trigonometric functions show their real potential in the manifold fields of applications. The most relevant of those are probably in the description of oscillation processes and wave phenomena in physics and engineering. However, they are also applied in many other fields as, for example, in geodesy and astronomy.