Tetraedrometry

As Tetraedrometrie (Greek.) It originally referred to the determination of the missing pieces of a three-sided pyramid , so a tetrahedron in a broader sense, given six pieces.

Since the end of the 19th century , tetraedrometry has been the theory of corner functions , by which three-sided corners are represented for calculation in a similar way as angles are represented by their trigonometric functions.