History of Science and Engineering Annotation << Back Element's of the right angle O.O. Barabanov Elements of the right angles history is presented. This story is explored in the following sequence: Primitive culture, Ancient Babylon, Ancient Egypt, Ancient India, Ancient Greece, the Middle Ages, the Renaissance, etc. An analysis of the following issues is first presented: the origin of the right angle in Primitive culture, right angle as a sign of civilization , the classification of right angles, a comparison of the accuracy of the Egyptian and Greek methods for constructing a right angle, the right angle in a Christian culture. Separately allocated extreme property right angle and the value of this property for optimal organization of the land cadastre of Ancient Babylon and Ancient Egypt. The article also contains some new historical additions to the theorems of a right triangle. The article ends with an open question: who first used the term «Hilbert space» in the modern sense? Keywords: symmetry; right angle; civilizational sign; classification; standard deviation; try square. Contacts: E-mail: barabanovoo@yandex.ru Pp. 16-27.