Trigonometry originated in ancient Greece. In order to predict the running route of celestial bodies, calculate the calendar, navigate and other needs, the ancient Greeks studied the relationship between the angles of a spherical triangle, and mastered the theorems that the sum of two sides of a spherical triangle is greater than the third side, the sum of the internal angles of a spherical triangle is greater than two right angles, and the angles are equal. Indians and Arabs also studied and popularized trigonometry, but it was mainly used in astronomy. In the 15 and 16 centuries, the study of trigonometry shifted to the plane triangle to achieve the purpose of measurement application. /kloc-The Vedas, a French mathematician in the 6th century, systematically studied plane triangles. He published a book about the mathematical laws applied to triangles. From then on, the plane triangle was separated from astronomy and became an independent branch. The contents of plane trigonometry mainly include trigonometric functions, solving triangles and trigonometric equations.

Triangulation also appeared very early in China, and it was explained in detail in the classic Weekly Parallel Computation as early as 100 BC. For example, in its first chapter, it is recorded that "Duke Zhou said," You are a good talker, so please use a moment's method. Shang Gao said that the flat moment is to use straight cable, the moment is to suppress the height, the complex moment is to measure the depth, and the lying moment is to know the distance. "(The moment mentioned by Shang Gao refers to two squares with vertical sides used by workers today, and the general idea of Shang Gao is that the height, depth and width of the target can be measured by putting the squares in different positions. ) 1 century "Nine Chapters of Arithmetic" has a chapter devoted to measurement.

For more information, see the encyclopedia entry (resources link).