[gon]

19 กุมภาพันธ์
1549 Osiander wrote of Michael Stifel; "He has devised new numbers for the alphabet, namely the triangular numbers, and his fantasies are more absurd than before."

20 กุมภาพันธ์
1962 John Glenn is the first American to orbit earth. He orbited three times in his Mercury capsule in 4 hours and 55 minutes, with an average speed to 17,400 miles per hour.

21 กุมภาพันธ์
1591 Desargues born.

22 กุมภาพันธ์
1877 J.J. Sylvester, at a commencement address at Johns Hopkins, gave his view on the relation between teaching and research: "An eloquent mathematician must, from the nature of things, ever remain as rare a phenomenon as a talking fish, and it is certain that the more anyone gives himself up to the study of oratorial effect, the less he will find himself in a fit state of mind to mathematicize."

1903 Frank Plumpton Ramsey born.

23 กุมภาพันธ์
1826 Lobachevsky first announced his principles of non-Euclidean geometry. This was done in a talk at his home University of Kazan.

24 กุมภาพันธ์
1582 Pope Gregory VIII promulgated his calendar reform in the papal bull Inter gravissimus (of the gravest concern.) It took effect October 5, 1582

1878 Felix Bernstein born. In 1895 or 1896, while still a Gymnasium student, he volunteered to read the proofs of a paper of Georg Cantor on set theory. In the process of doing this the idea came to him one morning while shaving of how to prove what is now called the Cantor/ Bernstein theorem: If each of two sets is equivalent to a subset of the other, then they are equivalent.

25 กุมภาพันธ์
1709 G. Riccati born.
1870 Hermann Amandus Schwarz writes his friend Georg Cantor a letter containing the first rigorous proof of the theorem that if the derivative of a function vanishes then the function is constant.