3rd-century BC introductions

Trigonometry () is a branch of mathematics concerned with relationships between angles and side lengths of triangles. In particular, the trigonometric functions relate the angles of a right triangle with ratios of its side lengths. The field emerged in the Hellenistic world during the 3rd century BC from applications of geometry to astronomical studies. The Greeks focused on the calculation of chords, while mathematicians in India created the earliest-known tables of values for trigonometric ratios (also called trigonometric functions) such as sine.

writing system of the Maya civilization

calligraphic tool

device with multiple hooks attached to one end of a rope, generally used to temporarily secure one end of a rope, or to dredge for submerged objects