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3 Georg Ferdinand Ludwig Philipp Cantor ( March 3, 1845, St. Petersburg, Russia – January 6, 1918, Halle, Germany) was a German mathematician who is best known as the creator of set theory. He was born between 1809 and 1814 in Copenhagen, Denmark, and brought up in a Lutheran German mission in St. Petersburg. CopenhagenDenmarkGermanCopenhagenDenmarkGerman Georg Cantor's father was a Danish man of Lutheran religion. Danish His mother, Maria Anna Böhm, was born in St. Petersburg and came from an Austrian Roman Catholic family. Austrian In 1860, Cantor graduated with distinction from the Realschule in Darmstadt; his exceptional skills in mathematics, trigonometry in particular, were noted. In 1862, following his father's wishes, Cantor entered the Federal Polytechnic Institute in Zurich, today the ETH Zurich and began studying mathematics. trigonometry In 1867, Berlin granted him the Ph.D. for a thesis on number theory, De aequationibus secundi gradus indeterminatis. After teaching one year in a Berlin girls' school, Cantor took up a position at the University of Halle, where he spent his entire career. He was awarded the requisite habilitation for his thesis on number theory.

4 Cantor was promoted to Extraordinary Professor in 1872, and made full Professor in To attain the latter rank at the age of 34 was a notable accomplishment, but Cantor very much desired a chair at a more prestigious university, in particular at Berlin, then the leading German university.. However, Kronecker, who headed mathematics at Berlin until his death in 1891, and his colleague Hermann Schwarz were not agreeable to having Cantor as a colleague. In 1890, Cantor was instrumental in founding the Deutsche Mathematiker- Vereinigung, chaired its first meeting in Halle in 1891, and was elected its first president. In 1911, Cantor was one of the distinguished foreign scholars invited to attend the 500th anniversary of the founding of the University of St. Andrews in Scotland. Scotland Cantor retired in 1913, and suffered from poverty, even hunger, during World War I. The public celebration of his 70th birthday was cancelled because of the war. He died in the sanatorium where he had spent the final year of his life. World War IWorld War I

5 He was the first to see that infinite sets come in different sizes, as follows. He first showed that given any set A, the set of all possible subsets of A, called the power set of A, exists. He then proved that the power set of an infinite set A has a size greater than the size of A (this fact is now known as Cantor's theorem). Thus there is an infinite hierarchy of sizes of infinite sets, from which springs the transfinite cardinal and ordinal numbers, and their peculiar arithmetic. His notation for the cardinal numbers was the Hebrew letter aleph with a natural number subscript; for the ordinals he employed the Greek letter omega. ordinal numbersordinal numbers Cantor was the first to appreciate the value of one-to-one correspondences (hereinafter denoted "1-to-1") for set theory. He defined finite and infinite sets, breaking down the latter into denumerable and nondenumerable setsThere exists a 1-to-1 correspondence between any denumerable set and the set of all natural numbers; all other infinite sets are nondenumerable. He proved that the set of all rational numbers is denumerable, but that the set of all real numbers is not and hence is strictly bigger. The cardinality of the natural numbers is aleph- null; that of the reals is larger, and is at least aleph-one (the latter being the next smallest cardinal after aleph-null). Cantor was the first to show that there was more than one kind of infinity. In doing so, he became the first to invoke the notion of a 1-to-1 correspondence, albeit not calling it such. Between 1879 and 1884, Cantor published a series of six articles in Mathematische Annalen that together formed an introduction to his set theory. Cantor was the first to show that there was more than one kind of infinity. In doing so, he became the first to invoke the notion of a 1-to-1 correspondence. Cantor's work did attract favorable notice beyond Hilbert's celebrated encomium. In public lectures delivered at the first International Congress of Mathematicians, held in Zurich in 1897, Hurwitz and Hadamard both expressed their admiration for Cantor's set theory.

6 Georg Ferdinand Ludwig Philipp Cantor Born: 3 March 1845 in St Petersburg, Russia Died: 6 Jan 1918 in Halle, Germany

7 Richard Dedekind's father was a professor at the Collegium Carolinum in Brunswick. His mother was the daughter of a professor who also worked at the Collegium Carolinum. He attended school in Brunswick from the age of seven. The Collegium Carolinum was an educational institution between a high school and a university and he entered it in 1848 at the age of 16. In the autumn term of 1850, Dedekind attended his first course given by Gauss. It was a course on least squares and [1]:- Gauss In 1854 both Riemann and Dedekind were awarded their habilitation degrees within a few weeks of each other. Dedekind was then qualified as a university teacher and he began teaching at Göttingen giving courses on probability and geometry. Riemann

8 The idea that came to him on 24 November 1858 was that every real number r divides the rational numbers into two subsets, namely those greater than r and those less than r. Dedekind's brilliant idea was to represent the real numbers by such divisions of the rationals. The Collegium Carolinum in Brunswick had been upgraded to the Brunswick Polytechnikum by the 1860s, and Dedekind was appointed to the Polytechnikum in 1862 As well as his analysis of the nature of number, his work on mathematical induction, including the definition of finite and infinite sets, and his work in number theory, particularly in algebraic number fields, is of major importance. It was in the third and fourth editions of Vorlesungen über Zahlentheorie, published in 1879 and 1894, that Dedekind wrote supplements in which he introduced the notion of an ideal which is fundamental to ring theory. Dedekind formulated his theory in the ring of integers of an algebraic number field. He presented a logical theory of number and of complete induction, presented his principal conception of the essence of arithmetic, and dealt with the role of the complete system of real numbers in geometry in the problem of the continuity of space. Among other things, he provides a definition independent of the concept of number for the infiniteness or finiteness of a set by using the concept of mapping and treating the recursive definition, which is so important to the theory of ordinal numbers. Dedekind's brilliance consisted not only of the theorems and concepts that he studied but, because of his ability to formulate and express his ideas so clearly, he introduced a new style of mathematics that been a major influence on mathematicians ever since.

9 Julius Wilhelm Richard Dedekind Born: 6 Oct 1831 in Braunschweig,Germany Died: 12 Feb 1916 in Braunschweig,Germany

10 Archimedes of Syracuse (Greek: ρχιμήδης) (c. 287 BC – c. 212 BC) was a Greek mathematician, physicist, engineer, inventor, and astronomer. Greek ρχιμήδηςGreek mathematician physicistengineerinventorastronomerGreek ρχιμήδηςGreek mathematician physicistengineerinventorastronomer Archimedes is considered to be one of the greatest mathematicians of all time.[2] He used the method of exhaustion to calculate the area under the arc of a parabola with the summation of an infinite series, and gave a remarkably accurate approximation of Pi.[3] He also defined the spiral bearing his name, formulas for the volumes of surfaces of revolution and an ingenious system for expressing very large numbers mathematicians[2] method of exhaustionareaparabolasummation of an infinite seriesPi[3] spiralvolumessurfaces of revolutionmathematicians[2] method of exhaustionareaparabolasummation of an infinite seriesPi[3] spiralvolumessurfaces of revolution Archimedes was born c. 287 BC in the seaport city of Syracuse, Sicily, at that time a colony of Magna Graecia Syracuse, SicilyMagna GraeciaSyracuse, SicilyMagna Graecia A biography of Archimedes was written by his friend Heracleides but this work has been lost, leaving the details of his life obscure.[8] It is unknown, for instance, whether he ever married or had children [8] Archimedes died c. 212 BC during the Second Punic War, when Roman forces under General Marcus Claudius Marcellus captured the city of Syracuse after a two-year-long siege. According to the popular account given by Plutarch, Archimedes was contemplating a mathematical diagram when the city was captured. A Roman soldier commanded him to come and meet General Marcellus but he declined, saying that he had to finish working on the problem. The soldier was enraged by this, and killed Archimedes with his sword. Second Punic War Marcus Claudius MarcellussiegeSecond Punic War Marcus Claudius Marcellussiege

11 While he is often regarded as a designer of mechanical devices, Archimedes also made contributions to the field of mathematics. Archimedes was able to use infinitesimals in a way that is similar to modern integral calculus. By assuming a proposition to be true and showing that this would lead to a contradiction, he could give answers to problems to an arbitrary degree of accuracy, while specifying the limits within which the answer lay. This technique is known as the method of exhaustion, and he employed it to approximate the value of π (Pi ) infinitesimalsintegral calculuscontradictionmethod of exhaustionπinfinitesimalsintegral calculuscontradictionmethod of exhaustionπ In The Measurement of a Circle, Archimedes gives the value of the square root of 3 as being more than 265/153 (approximately ) and less than 1351/780 (approximately ). The actual value is approximately , making this a very accurate estimate. square rootsquare root In The Quadrature of the Parabola, Archimedes proved that the area enclosed by a parabola and a straight line is 4/3 multiplied by the area of a triangle with equal base and height. He expressed the solution to the problem as a geometric series that summed to infinity with the ratio 1/4: The Quadrature of the Parabolaparabolatrianglegeometric seriessummed to infinity ratioThe Quadrature of the Parabolaparabolatrianglegeometric seriessummed to infinity ratio If the first term in this series is the area of the triangle, then the second is the sum of the areas of two triangles whose bases are the two smaller secant lines, and so on. This proof is a variation of the infinite series 1/4 + 1/16 + 1/64 + 1/256 + · · · which sums to 1/3. secant linesinfinite series1/4 + 1/16 + 1/64 + 1/256 + · secant linesinfinite series1/4 + 1/16 + 1/64 + 1/256 + · Archimedes devised a system of counting based on the myriad. The word is from the Greek μυριάς murias, for the number 10,000. He proposed a number system using powers of a myriad of myriads (100 million) and concluded that the number of grains of sand required to fill the universe would be 8×1063, which can also be expressed as eight vigintillion. [35] myriadvigintillion[35]myriadvigintillion[35]

12 Surviving works On plane equilibriums, Quadrature of the parabola, On the sphere and cylinder, On spirals, On conoids and spheroids, On floating bodies, Measurement of a circle, The Sandreckoner, On the method of mechanical problems. Place in History Generally regarded as the greatest mathematician and scientist of antiquity and one of the three greatest mathematicians of all time (together with Isaac Newton (English ) and Carl Friedrich Gauss (German )). Isaac Newton Carl Friedrich Gauss Isaac Newton Carl Friedrich Gauss

13 Archimedes of Syracuse Born: 287 BC in Syracuse, Sicily Died: 212 BC in Syracuse, Sicily



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