The method of using ∑ to represent ∑ symbol is called Sigma symbol, or Sigma Notation. Its lowercase is σ, which is often used in physics to represent the area density. (Accordingly, ρ stands for bulk density and η stands for linear density).
In chemistry, we use its lowercase letter σ to represent a valence bond. The valence bond formed by the overlapping of two atomic orbits along the direction of orbital symmetry axis increases the probability of electrons appearing between nuclei, which is called σ bond. σ bond is a localized bond, which can be a general valence bond or a coordination valence bond. Generally, single bonds are σ bonds.
Capital σ is used for mathematical summation symbols, such as ∑Pi, where i= 1, 2, ..., t, which is the sum of P 1+P2+ and ...+angle. Lowercase σ is used for statistical standard deviation. Both the с of Cyrillic alphabet and the S of Latin alphabet are derived from Sigma. It also means summation, which means ∑j= 1+2+3+ ...
As follows:
Mathematics (Mathematics or maths, from the Greek word "Má thē ma"; Often abbreviated as "mathematics"), it is a discipline that studies concepts such as quantity, structure, change, space and information, and belongs to a formal science from a certain point of view. Mathematicians and philosophers have a series of views on the exact scope and definition of mathematics.
In the development of human history and social life, mathematics also plays an irreplaceable role, and it is also an indispensable basic tool for studying and studying modern science and technology.
The study of space originates from Euclidean geometry, while trigonometry combines space with numbers, including the famous Pythagorean theorem, trigonometric function and so on. Now the research on space is extended to high-dimensional geometry, non-Euclidean geometry and topology. Numbers and spaces play an important role in analytic geometry, differential geometry and algebraic geometry. In differential geometry, there are concepts such as fiber bundle and calculation on manifold.