[Father of Russian mathematics — 200th anniversary] Chebyshev P. L. A set of six separate offprints from the 1860-1880s.

Pafnuty Lvovich Chebyshev (1821 –1894) — a Russian mathematician considered to be the founding father of Russian mathematics. Chebyshev is known for his fundamental contributions to the fields of probability, statistics, mechanics, and number theory. A number of important mathematical concepts were named after him, including the Chebyshev inequality (which can be used to prove the weak law of large numbers), the Bertrand–Chebyshev theorem, Chebyshev polynomials, and Chebyshev bias. (Chebyshev is known for his work in the fields of probability, statistics, mechanics, and number theory.) Предлагаю последнее предложение убрать, так как оно дублирует одно из предыдущих. 

Of Chebyshev's numerous discoveries, it is necessary to mention first of all the works on number theory. They began with Chebyshev's doctoral dissertation "The Theory of Comparisons", published in 1849; it became the first Russian monograph on number theory. In 1851, his famous memoir "On Determining the Number of Primes that Do not Exceed a Given Value" appeared. By this time, the unproven Legendre hypothesis was known, Chebyshev discovered a much better approximation — the integral logarithm. This memoir brought the 30-year-old Chebyshev pan-European fame.

In the following year, 1852, Chebyshev published a new article "On Prime Numbers". In it, he conducted a deep analysis of the convergence of series that depend on prime numbers, found a criterion for their convergence. As an application of these results, he proved for the first time the "Bertrand postulate".

Chebyshev worked a lot on the theory of quadratic forms and related problems of divisibility of natural numbers and their decomposition into prime factors. In his 1866 article "On an arithmetic question", he used the apparatus of continuous fractions to investigate Diophantine approximations of integers. In analytical number theory, he was one of the first to use the gamma function.

Chebyshev became the first world-class Russian mathematician in probability theory. Since 1860, he replaced V. I. Bunyakovsky at the Department of Probability Theory of St. Petersburg University and began his series of lectures. He published only four works on this topic, but of a fundamental nature. In the article "On Average Values" (1866), the "Chebyshev inequality" was first proved. In the same article, P. L. Chebyshev for the first time clearly justified the generally accepted point of view on the concept of a random variable as one of the basic concepts of probability theory. Although the theory of approximation of functions has a fairly rich background, the actual history of this section of mathematics has been calculated since 1854, when P. L. Chebyshev's article "The Theory of Mechanisms Known as Parallelograms" was published. It was the first of a series of works by the scientist on "functions that least deviate from zero" (Chebyshev devoted forty years to research in this area).

Chebyshev owns a theorem on the integrability conditions of a differential binomial, published in his 1853 memoir "On the Integration of Irrational Differentials". In 1859, in the article "On the Decomposition of Functions of One Variable", Chebyshev introduced two new systems of classical orthogonal polynomials. They are now known as Chebyshev-Hermite polynomials (or Hermite polynomials) and Chebyshev-Laguerre polynomials (or Laguerre polynomials). All these systems of orthogonal polynomials play an important role in mathematics, having diverse applications. At the same time, Chebyshev developed a general theory of decomposition of an arbitrary function into a series of orthogonal polynomials based on the apparatus of continuous fractions

For forty years Chebyshev took an active part in the work of the military artillery. In the courses of ballistics, the Chebyshev's formula for calculating the range of a projectile depending on its throwing angle, initial velocity and air resistance at a given initial velocity has been preserved to this day. Chebyshev's article with an unusual title "On Cutting Clothes" (1878) was devoted to the differential geometry of surfaces; in it, the scientist introduced a new class of coordinate grids, called "Chebyshev networks". () ( ) Chebyshev also laid the foundation for the theory of the structure of plane mechanisms. In his work "On Parallelograms" (1869), he derived a structural formula for lever mechanisms with rotational kinematic pairs and one degree of freedom (now known as the "Chebyshev formula"). He owns the creation of more than 40 different mechanisms and about 80 of their modifications. Among them are mechanisms with stops, mechanisms of rectifiers and accelerators of movement and similar mechanisms, many of which are used in modern auto, motorcycle and instrument making.

Chebyshev was the first person to think systematically in terms of random variables and their moments and expectations. Chebyshev is considered to be a founding father of Russian mathematics. Among his well-known students were the mathematicians Dmitry Grave, Aleksandr Korkin, Aleksandr Lyapunov, and Andrei Markov. According to the Mathematics Genealogy Project, Chebyshev has 13,709 mathematical "descendants" as of January 2020.

Six separate prints from the 1860-1880s. 

About an Arithmetic Question. St. Petersburg, 1866, 54 p.

On Integral Deductions Delivering Approximate Values of Integrals. St. Petersburg, 1887, 50 p.

About Parallelograms Consisting of Three Elements of Any Kind. St. Petersburg, 1880, 40 p.

On Approximate Expressions of the Square Root of a Variable in Terms of Simple Fractions. St. Petersburg, 1889, 22 p.

About Interpolation. St. Petersburg, 1864, 23 p.

On the Representation of Limit Values. St. Petersburg, 1885, 25 p.