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Musselman's Theorem
In Euclidean geometry, Musselman's theorem is a property of certain circles defined by an arbitrary triangle. Specifically, let T be a triangle, and A, B, and C its vertices. Let A^*, B^*, and C^* be the vertices of the reflection triangle T^*, obtained by mirroring each vertex of T across the opposite side. Let O be the circumcenter of T. Consider the three circles S_A, S_B, and S_C defined by the points A\,O\,A^*, B\,O\,B^*, and C\,O\,C^*, respectively. The theorem says that these three Musselman circles meet in a point M, that is the inverse with respect to the circumcenter of T of the isogonal conjugate or the nine-point center of T. The common point M is point X_ in Clark Kimberling's list of triangle centers. History The theorem was proposed as an advanced problem by John Rogers Musselman and René Goormaghtigh in 1939, and a proof was presented by them in 1941. A generalization of this result was stated and proved by Goormaghtigh. Goormaghtigh’s generalizat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Euclidean Geometry
Euclidean geometry is a mathematical system attributed to ancient Greek mathematics, Greek mathematician Euclid, which he described in his textbook on geometry: the ''Euclid's Elements, Elements''. Euclid's approach consists in assuming a small set of intuitively appealing axioms (postulates) and deducing many other propositions (theorems) from these. Although many of Euclid's results had been stated earlier,. Euclid was the first to organize these propositions into a logic, logical system in which each result is ''mathematical proof, proved'' from axioms and previously proved theorems. The ''Elements'' begins with plane geometry, still taught in secondary school (high school) as the first axiomatic system and the first examples of mathematical proofs. It goes on to the solid geometry of three dimensions. Much of the ''Elements'' states results of what are now called algebra and number theory, explained in geometrical language. For more than two thousand years, the adjective " ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Triangle Center
In geometry, a triangle center (or triangle centre) is a point in the plane that is in some sense a center of a triangle akin to the centers of squares and circles, that is, a point that is in the middle of the figure by some measure. For example, the centroid, circumcenter, incenter and orthocenter were familiar to the ancient Greeks, and can be obtained by simple constructions. Each of these classical centers has the property that it is invariant (more precisely equivariant) under similarity transformations. In other words, for any triangle and any similarity transformation (such as a rotation, reflection, dilation, or translation), the center of the transformed triangle is the same point as the transformed center of the original triangle. This invariance is the defining property of a triangle center. It rules out other well-known points such as the Brocard points which are not invariant under reflection and so fail to qualify as triangle centers. For an equilateral triangle, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Forum Geometricorum
''Forum Geometricorum: A Journal on Classical Euclidean Geometry'' is a peer-reviewed open-access academic journal that specializes in mathematical research papers on Euclidean geometry. It was founded in 2001, is published by Florida Atlantic University Florida Atlantic University (Florida Atlantic or FAU) is a public research university with its main campus in Boca Raton, Florida, and satellite campuses in Dania Beach, Davie, Fort Lauderdale, Jupiter, and Fort Pierce. FAU belongs to the 12-ca ..., and is indexed among others by Mathematical Reviews and . Its founding editor-in-chief was Paul Yiu, a professor of mathematics at Florida Atlantic, now retired. All papers are available online immediately upon acceptance through the journal's web site. , Forum Geometricorum is no longer accepting submissions. Prior issues are still available. See also * International Journal of Geometry References External links * {{official website, http://forumgeom.fau.edu/ Mathematic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Euler Line
In geometry, the Euler line, named after Leonhard Euler (), is a line determined from any triangle that is not equilateral. It is a central line of the triangle, and it passes through several important points determined from the triangle, including the orthocenter, the circumcenter, the centroid, the Exeter point and the center of the nine-point circle of the triangle. The concept of a triangle's Euler line extends to the Euler line of other shapes, such as the quadrilateral and the tetrahedron. Triangle centers on the Euler line Individual centers Euler showed in 1765 that in any triangle, the orthocenter, circumcenter and centroid are collinear. This property is also true for another triangle center, the nine-point center, although it had not been defined in Euler's time. In equilateral triangles, these four points coincide, but in any other triangle they are all distinct from each other, and the Euler line is determined by any two of them. Other notable points that lie on ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Joseph Jean Baptiste Neuberg
Joseph Jean Baptiste Neuberg (30 October 1840 – 22 March 1926) was a Luxembourger mathematician who worked primarily in geometry. Biography Neuberg was born on 30 October 1840 in Luxembourg City, Luxembourg. He first studied at a local school, the Athénée de Luxembourg, then progressed to Ghent University, studying at the École normale des Sciences of the science faculty. After graduation, Neuberg taught at several institutions. Between 1862 and 1865, he taught at the École Normale de Nivelle. For the next sixteen years, he taught at the Athénée Royal d'Arlon, though he also taught at the École Normale at Bruges from 1868 onwards. Retrieved on 2008-09-16. Neuberg switched from his previous two schools to the Athénée Royal de Liège in 1878. He became an extraordinary professor in the university in the same city in 1884, and was promoted to ordinary professor in 1887. He held this latter position until his retirement in 1910. A year after his retirement, he was elect ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Altitude (triangle)
In geometry, an altitude of a triangle is a line segment through a vertex and perpendicular to (i.e., forming a right angle with) a line containing the base (the side opposite the vertex). This line containing the opposite side is called the ''extended base'' of the altitude. The intersection of the extended base and the altitude is called the ''foot'' of the altitude. The length of the altitude, often simply called "the altitude", is the distance between the extended base and the vertex. The process of drawing the altitude from the vertex to the foot is known as ''dropping the altitude'' at that vertex. It is a special case of orthogonal projection. Altitudes can be used in the computation of the area of a triangle: one half of the product of an altitude's length and its base's length equals the triangle's area. Thus, the longest altitude is perpendicular to the shortest side of the triangle. The altitudes are also related to the sides of the triangle through the trigonometri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orthocenter
In geometry, an altitude of a triangle is a line segment through a vertex and perpendicular to (i.e., forming a right angle with) a line containing the base (the side opposite the vertex). This line containing the opposite side is called the ''extended base'' of the altitude. The intersection of the extended base and the altitude is called the ''foot'' of the altitude. The length of the altitude, often simply called "the altitude", is the distance between the extended base and the vertex. The process of drawing the altitude from the vertex to the foot is known as ''dropping the altitude'' at that vertex. It is a special case of orthogonal projection. Altitudes can be used in the computation of the area of a triangle: one half of the product of an altitude's length and its base's length equals the triangle's area. Thus, the longest altitude is perpendicular to the shortest side of the triangle. The altitudes are also related to the sides of the triangle through the trigonometri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
René Goormaghtigh
René Goormaghtigh (13 October 1893, Ostend – 10 February 1960, Ixelles) was a Belgian engineer, after whom the Goormaghtigh Conjecture is named. Goormaghtigh studied at Ghent University, gaining a Diploma in Civil Engineering from the Central Board of Le Havre in 1918. Throughout his subsequent life he worked as an engineer and industrial administrator. In 1952 he was appointed advisor to the Société Générale de Belgique. He was made a Knight of the Order of Leopold II The Order of Leopold II is an order of Belgium and is named in honor of King Leopold II. The decoration was established on 24 August 1900 by Leopold II as Sovereign of the Congo Free State and was in 1908, upon Congo being handed over to Belgium ... in 1947, and an Officer of the Order of the Crown in 1956. After a heart attack in 1958, he retired to Saint-André-des-Bruges.Fransisco Bellot-RosadoRené Gormaghtigh, ingénieur et géomètre de MATHESIS/ref> He was a frequent contributor to mathematical jo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
John Rogers Musselman
John Rogers Musselman (1 December 1890, Gettysburg, Pennsylvania – 8 August 1968, Cleveland) was an American mathematician, specializing in algebraic geometry and known for Musselman's theorem. J. R. Musselman received his A.B. in 1910 from Pennsylvania College and his Ph.D. from Johns Hopkins University in 1916 under Arthur Byron Coble with thesis ''A set of eight self-associated points in space''. Musselman was a teaching assistant at Gettysburg Academy from 1910 to 1912 and an instructor in mathematics at the University of Illinois in 1916–1918 and then at Washington University in St. Louis in 1920–1928. He was a professor mathematics at Western Reserve University from 1928 until his retirement as professor emeritus in 1961. He was an Invited Speaker of the International Congress of Mathematicians in 1936 in Oslo. Selected publications"Spurious Correlation Applied to Urn Schemata."Journal of the American Statistical Association 18, no. 143 (1923): 908–911. *"On the li ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kimberling Center
The Encyclopedia of Triangle Centers (ETC) is an online list of thousands of points or " centers" associated with the geometry of a triangle. It is maintained by Clark Kimberling, Professor of Mathematics at the University of Evansville. , the list identifies 52,440 triangle centers. Each point in the list is identified by an index number of the form ''X''(''n'')—for example, ''X''(1) is the incenter. The information recorded about each point includes its trilinear and barycentric coordinates and its relation to lines joining other identified points. Links to The Geometer's Sketchpad diagrams are provided for key points. The Encyclopedia also includes a glossary of terms and definitions. Each point in the list is assigned a unique name. In cases where no particular name arises from geometrical or historical considerations, the name of a star is used instead. For example, the 770th point in the list is named ''point Acamar''. The first 10 points listed in the Encyclopedia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Circle (geometry)
A circle is a shape consisting of all points in a plane that are at a given distance from a given point, the centre. Equivalently, it is the curve traced out by a point that moves in a plane so that its distance from a given point is constant. The distance between any point of the circle and the centre is called the radius. Usually, the radius is required to be a positive number. A circle with r=0 (a single point) is a degenerate case. This article is about circles in Euclidean geometry, and, in particular, the Euclidean plane, except where otherwise noted. Specifically, a circle is a simple closed curve that divides the plane into two regions: an interior and an exterior. In everyday use, the term "circle" may be used interchangeably to refer to either the boundary of the figure, or to the whole figure including its interior; in strict technical usage, the circle is only the boundary and the whole figure is called a '' disc''. A circle may also be defined as a special ki ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nine-point Center
In geometry, the nine-point center is a triangle center, a point defined from a given triangle in a way that does not depend on the placement or scale of the triangle. It is so called because it is the center of the nine-point circle, a circle that passes through nine significant points of the triangle: the midpoints of the three edges, the feet of the three altitudes, and the points halfway between the orthocenter and each of the three vertices. The nine-point center is listed as point X(5) in Clark Kimberling's Encyclopedia of Triangle Centers..Encyclopedia of Triangle Centers accessed 2014-10-23. Properties The nine-point center lies on the of its triangle, a ...[...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
