January brought nice surprises to me. I had no idea that two of my favorite mathematicians are born in January and also the birthdays are so close to each other in term of days, obviously not years. Moreover, I have found another interesting mathematician (new to me) which was also born in January. So I thought it is absolutely necessary to write a small post about them.

**Joseph-Louis Lagrange**, born on 25 January 1736, was an Italian Enlightenment Era mathematician and astronomer. He made significant contributions to the fields of analysis, number theory, and both classical and celestial mechanics.

At first I was surprised to see that he is Italian because all my life I was sure he is French. To my surprise, i have found that he was born in Turin ( the former capital of Italy near the French border) and even did his studies there. His real name was Giuseppe Luigi Lagrangia. He went to university of Turin to become a lawyer, but changed his mind for mathematics when he was 17-18. Quite interesting, but he moved to Berlin first and then much later to Paris at the call of Louis XVI, when he transformed his name to the one we know today.

Lagrange was one of the creators of the calculus of variations, deriving the Euler–Lagrange equations for extrema of functionals. He also extended the method to take into account possible constraints, arriving at the method of Lagrange multipliers. Lagrange invented the method of solving differential equations known as variation of parameters, applied differential calculus to the theory of probabilities and attained notable work on the solution of equations. He proved that every natural number is a sum of four squares. His treatise “Theorie des fonctions analytiques” laid some of the foundations of group theory, anticipating Galois. In calculus, Lagrange developed a novel approach to interpolation and Taylor series. He studied the three-body problem for the Earth, Sun and Moon (1764) and the movement of Jupiter’s satellites (1766), and in 1772 found the special-case solutions to this problem that yield what are now known as Lagrangian points. Also, he has transformed Newtonian mechanics into a branch of analysis, Lagrangian mechanics as it is now called, and presented the so-called mechanical “principles” as simple results of the variational calculus.

**David Hilbert**, born on 23rd January 1862, was a German mathematician. He is recognized as one of the most influential and universal mathematicians of the 19th and early 20th centuries. Hilbert discovered and developed a broad range of fundamental ideas in many areas, including invariant theory and the axiomatization of geometry. He also formulated the theory of Hilbert spaces, one of the foundations of functional analysis.

Hilbert adopted and warmly defended Georg Cantor’s set theory and transfinite numbers. A famous example of his leadership in mathematics is his 1900 presentation of a collection of problems that set the course for much of the mathematical research of the 20th century.

Hilbert and his students contributed significantly to establishing rigor and developed important tools used in modern mathematical physics. Hilbert is known as one of the founders of proof theory and mathematical logic, as well as for being among the first to distinguish between mathematics and metamathematics.

And the last, but not the least and my new discovery for this month: Frigyes Riesz.

**Frigyes Riesz**, born on 22 January 1880, was a Hungarian mathematician who made fundamental contributions to functional analysis.

Riesz did some of the fundamental work in developing functional analysis and his work has had a number of important applications in physics. He established the spectral theory for bounded symmetric operators in a form very much like that now regarded as standard. He also made many contributions to other areas including ergodic theory.

He had an uncommon method of giving lectures if you ask me. He entered the lecture hall with an assistant and a docent. The docent then began reading the proper passages from Riesz’s handbook and the assistant inscribed the appropriate equations on the blackboard —while Riesz himself stood aside, nodding occasionally. Quite some funny lectures ^_^

*Source : Wikipedia*

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*Don’t forget that maths is everywhere! Enjoy! ~LThMath~*

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