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Division of angles and circles

(923 words)

Author(s): Folkerts, Menso (Munich)
[German version] I. Ancient Orient see  Mathematics I Folkerts, Menso (Munich) II. Classical Antiquity [German version] A. Division of circles The division of circles, i.e. the division of the circumference of a circle into any number of arcs of equal length, is directly correlated to the regular polygons: if a regular n-gon is inscribed in a circle, the circumference of the circle is divided into n sections and the angle at the centre belonging to the side of the n-gon has the value 360°/ n . The Pythagoreans ( Pythagoras [2]) were already interested in the regular polygons a…


(385 words)

Author(s): Folkerts, Menso (Munich)
[German version] (Δεινόστρατος; Deinóstratos) D. is mentioned in Eudemus' list of mathematicians as the brother of Menachmus, who was a pupil of Eudoxus (Procl. in primum Euclidis elementorum librum comm., p. 67,11 Friedlein). He therefore lived in the middle of the 4th cent. BC  Pappus of Alexandria reports (4,30, p. 250,33-252,3 Hultsch) that to square the circle D. used a curve that was accordingly called the quadratrix (τετραγωνίζουσα). This curve, said to have already been used by Hippias of Elis for the trisection…


(162 words)

Author(s): Folkerts, Menso (Munich)
[German version] (Θυμαρίδας; Thymarídas). Mathematician from Paros; according to Iamblichus (v. P. 104), T. was an early Pythagorean (Pythagorean School). He defined 'unity' (μονάς/ monás; i.e. the One that generates all the natural numbers) as περαίνουσα ποσότης ( peraínousa posótēs, 'limiting quantity'; Iambl. in Nicomachi arithmeticam introductionem 11,2-5) and called prime numbers εὐθυγραμμικός ( euthygrammikós, 'rectilinear'; ibid.  27,4), because they can only be set out in one dimension. The name 'Flower of T.' (Θυμαρίδειον ἐπάνθημα, Thymarídeion epánthēma) is gi…


(603 words)

Author(s): Folkerts, Menso (Munich)
[German version] (Ὑψικλῆς; Hypsiklês). Hellenistic mathematician and astronomer. From the introduction to book 14 of Euclid's ‘Elements’ written by him, it follows that H. lived in Alexandria around 175 BC. It is attested by MSS that he composed what later was added as book 14 to the ‘Elements’ of  Euclides [3] (ed. [1]). Like bk. 13 it deals with the inscribing of regular bodies into a sphere and was thought of as an explanation to a lost work of  Apollonius [13] about dodecahedra and icosahedra. H. shows that the planes th…

Pappus of Alexandria

(727 words)

Author(s): Folkerts, Menso (Munich)
(Πάππος Ἀλεξανδρεύς; Páppos Alexandreús). [German version] I. Life Eminent Greek mathematician. Based on his calculation of a partial solar eclipse for the year AD 320, it is assumed that P. lived in the first half of the 4th cent. (on this and on erroneous dating in the Suda see [2. 2-4]). Folkerts, Menso (Munich) [German version] II. Works The most important surviving work is the Συναγωγή/ Synagōgḗ, customarily cited as the Collectio (ed. [1], French translation [3], edition and English translation of book 7 [2]). Of the 8 books, the first is wholly lost, the se…

Duplication of the Cube

(1,109 words)

Author(s): Folkerts, Menso (Munich)
(κύβου διπλασιασμός/ kýbou diplasiasmós according to Eratosthenes, in [1. 88,16]). [German version] I. General The duplication of the cube ─ besides the  division of angles and circles and the  squaring of the circle ─ belongs to the three classic problems in Greek  mathematics. The challenge is such: to find ─ through the use of geometry ─ for a given cube with a side-length of a (and thus the volume of a 3) the side x of another cube whose volume is twice as big as that of the given cube. The problem is therefore to find the value of x, to which applies: x 3 = 2 a 3 (that is: x = a 32). The problem thus…

Land surveying

(895 words)

Author(s): Folkerts, Menso (Munich)
[English version] The writings of the Roman surveyors ( agrimensores) deal with their various areas of activity: measurement of areas; limitation, i.e. division by orthogonal boundaries; creation of land registers and general parceling maps; functioning as a judges or experts in land law, particularly in boundary disputes; collaboration in religious ceremonies; units of length and area, weights and determining area and volume. Mathematical questions are dealt with most notably by Balbus' work Expositio et ratio omnium formarum (ca . AD 100), the anonymous Liber podismi and a wo…


(99 words)

Author(s): Folkerts, Menso (Munich)
[German version] (μεσολάβιον; mesolábion). A mechanical device invented by Eratosthenes [2] to establish graphically the two geometric means x and y between two given lines a and b (as in the relationship a: x = x: y = y: b). The mesolabium enabled the mechanical solution of the problem of the duplication of the cube (‘Delian problem’): if b = 2 a, then x is the desired solution of the equation for the duplication of the cube ( x3 = 2a3 ). Hippocrates [5] of Chios Folkerts, Menso (Munich) Bibliography mes T. L. Heath, A History of Greek Mathematics, Vol. 2, 1921, 258-260.


(103 words)

Author(s): Folkerts, Menso (Munich)
(ῥόμβος/ rhómbos). [German version] [1] Geometric shape In the plane, a rectangle with four sides of equal length but with unequal angles ( i.e., with two acute and two obtuse angles; Euc. 1, Def. 22; Censorinus, DN 83,14 Jahn). In three dimensions, a rhombus is the solid of revolution consisting of two cones with the same base (Archim. De sphaera et cylindro 1, def. 6). Folkerts, Menso (Munich) Bibliography 1 T. L. Heath, The Thirteen Books of Euclid's Elements, vol. 1, 21925, 189 2 A. Hug, s.v. Ῥόμβος ( rhombus), RE 1 A, 1069. [German version] [2] See Top see Top [German version] [3] See Rho…


(124 words)

Author(s): Folkerts, Menso (Munich)
[German version] (νεῦσις/ neûsis, ‘inclination’, in the mathematical sense: ‘verging’) is a geometric operation that cannot be performed with a compass and ruler alone. It allows problems  that lead to cubic and other higher equations (for example, cube duplication, angle trisection, squaring the circle) to be solved geometrically. A neûsis construction is necessary when a straight line through a given point is supposed to intersect two given lines so that the distance between the points of intersection is equal to a certain distance. Nicomede…

Quadrature of the circle

(1,369 words)

Author(s): Folkerts, Menso (Munich)
(ὁ τοῦ κύκλου τετραγωνισμός/ ho toû kýklou tetragōnismós, Latin quadratura circuli). [German version] I. The nature of the problem The quadrature of the circle is one of the three 'classic problems' (the other two being the trisection of an angle, cf. division of angles and circles, and the duplication of the cube) of ancient Greek mathematics. The problem is to find the side x of a square such that its area is equal to the area of a circle with radius r using a geometric procedure; that is,  to determine the value of the variable x in the equation x 2 = π r 2. Accordingly, the solution to the q…


(210 words)

Author(s): Folkerts, Menso (Munich)
[German version] (Θεύδιος; Theúdios). Mathematician and philosopher from Magnesia, probably 4th century BC. The only information about him comes from the catalogue of mathematicians in Proclus's [2] commentary on Euclid [1. 67, Z. 12-20]. T. is mentioned there after Eudoxus [1] and before Philippus of Medma, who was a pupil of Plato [1]; Therefore, T. was probably a contemporary of Aristotle [6]. According to Proclus, T., Menaechmus [3] and Deinostratus conducted research together at the Academy ( Akadḗmeia ), improved the arrangement of the 'Elements', and put many limited pr…


(168 words)

Author(s): Folkerts, Menso (Munich)
[German version] (Eυτόκιος; Eutókios) The mathematician E. of Ascalon was presumably born around AD 480; the widespread assumption that he was a pupil of the architect  Isidorus of Miletus is hardly plausible [1. 488]. He wrote commentaries on three works of  Archimedes [1] ( Perì sphaíras kaì kylíndrou, Περὶ σφαίρας καὶ κυλίνδρου, kýklou métrēsis, κύκλου μέτρησις, Perì epipédōn isorrhopiôn, Περὶ ἐπιπέδων ἰσορροπιῶν, text editions [3. 1-319]) as well as on the first four books of Apollonius' Kōniká (Κωνικά) [13] (dedicated to  Anthemius [3], text edition [4. 168-361]…


(272 words)

Author(s): Folkerts, Menso (Munich)
[German version] [1] see Groma see  Groma (surveying) Folkerts, Menso (Munich) [German version] [2] see Clocks see  Clocks (time measurement) Folkerts, Menso (Munich) [German version] [3] Arithmetic technical term Arithmetic technical term from Greek numerical theory. The term was adopted from geometry, where the gnomon describes the shape of an angle bar that remains when a smaller square is removed from a larger square. The Pythagoreans represented arithmetic series with geometrically arranged dots (pebbles) in the form of figures, so t…

Mechanical method

(255 words)

Author(s): Folkerts, Menso (Munich)
[German version] The ‘Method (Ἔφοδος; Éphodos) of Archimedes [1] is our source for his mechanical method from which he derived geometric formulas. To compare the surfaces of two figures, he disassembled each into an infinite number of parallel lines and balanced them on a scale. On one side of the scale, one surface is hung up at one point, i.e., as a whole. On the other side, the surface is hung up along the entire arm, i.e., each layer remains where it is and acts with a different leverage. When ea…


(143 words)

Author(s): Folkerts, Menso (Munich)
[German version] In the same way as postulates, axioms were presumably introduced in conflict with Eleatic philosophy in order to enable the acceptance of the existence of the manifold [1. 322-325; 2; 3]. According to Aristotle, axioms are central to every branch of knowledge, particularly the law of contradiction and the principle of the excluded middle (Metaph. Γ 3,1005a19-b27); for the organization of the fundamental principles of a branch of knowledge wherein proof is sought see Aristot. An. p…


(3,425 words)

Author(s): Folkerts, Menso (Munich)
Folkerts, Menso (Munich) [German version] A. Introduction (CT) Taking their point of departure from the mathematical accomplishments of the Egyptians and Babylonians, the Greeks remodelled mathematics into a deductive system based on a theory of proof. For the Greeks, unlike for their predecessors, mathematics was a science practiced for its own sake, which also investigated its own foundations; thus, practical considerations and directly numerical problems faded into the background. The main accomplish…


(734 words)

Author(s): Graf, Fritz (Columbus, OH) | Folkerts, Menso (Munich)
(Αὐτόλυκος; Autólykos). [German version] [1] Son of Hermes and Chione Son of Hermes and Chione (or Philonis, who also bore the singer  Philammon to Apollo, Hes. fr. 64,14). He was included in various mythical family circles, as the father of  Odysseus' mother Anticlea (Hom. Od. 11,85), of  Jason's mother Polymede (Apollod. 1,107) and of Aesimus, the father of  Sinon. He gives the newborn Odysseus his name, and it is whilst hunting with his sons on Mount Parnassus that Odysseus receives the wound in his th…


(196 words)

Author(s): Frey, Alexandra (Basle) | Folkerts, Menso (Munich)
(Κάρπος; Kárpos). [German version] [1] Son of Zephyrus and a certain Hore Handsome youth, son of Zephyrus and of a certain Hore ( Horae). He organizes a swimming race with  Calamus, his best friend, but drowns in the event. In mourning, his friend kills himself and is turned into reeds. C. is turned into a crop of the field (Nonnus, Dion. 11,385-481). Frey, Alexandra (Basle) [German version] [2] C. of Antioch Mathematician A mathematician, who lived presumably in the 1st or 2nd cent. AD. Information on him is given in four fragments by Pappus (8,3), Proclus (in Euc…


(2,119 words)

Author(s): Folkerts, Menso (Munich) | Degani, Enzo (Bologna)
[1] of Syracuse C. 287-232 BC [German version] A. Life A. was born in 287 BC in Syracuse, son of the astronomer Phidias. He was friends with King Hieron II, and later with his son Gelon. A. probably spent some time in Alexandria; he later sent on his writings to the mathematicians (Conon, Dositheus, Eratosthenes) who were working there. In Syracuse, A. studied problems of mathematical and physical theory, but also their practical applications; the machines and physical apparatus which he built (e.g. the s…
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