|
Cross Ratio
In geometry, the cross-ratio, also called the double ratio and anharmonic ratio, is a number associated with a list of four collinear points, particularly points on a projective line. Given four points , , , on a line, their cross ratio is defined as : (A,B;C,D) = \frac where an orientation of the line determines the sign of each distance and the distance is measured as projected into Euclidean space. (If one of the four points is the line's point at infinity, then the two distances involving that point are dropped from the formula.) The point is the Projective harmonic conjugate, harmonic conjugate of with respect to and precisely if the cross-ratio of the quadruple is , called the ''harmonic ratio''. The cross-ratio can therefore be regarded as measuring the quadruple's deviation from this ratio; hence the name ''anharmonic ratio''. The cross-ratio is preserved by linear fractional transformations. It is essentially the only projective invariant (mathematics), invarian ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Projection Geometry
Projection or projections may refer to: Physics * Projection (physics), the action/process of light, heat, or sound reflecting from a surface to another in a different direction * The display of images by a projector Optics, graphics, and cartography * Map projection, reducing the surface of a three-dimensional planet to a flat map * Graphical projection, the production of a two-dimensional image of a three-dimensional object Chemistry * Fischer projection, a two-dimensional representation of a three-dimensional organic molecule * Haworth projection, a way of writing a structural formula to represent the cyclic structure of monosaccharides * Natta projection, a way to depict molecules with complete stereochemistry in two dimensions in a skeletal formula * Newman projection, a visual representation of a chemical bond from front to back Mathematics * Projection (mathematics), any of several different types of geometrical mappings ** Projection (linear algebra), a linear tran ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Robert Simson
Robert Simson (14 October 1687 – 1 October 1768) was a Scottish mathematician and professor of mathematics at the University of Glasgow. The Simson line is named after him.Robert Simson University of Glasgow (multi-tab page) Biography Robert Simson was born on 14 October 1687, probably the eldest of the seventeen children, all male, of John Simson, a Glasgow merchant, and Agnes, daughter of Patrick Simpson, minister of Renfrew; only six of them reached adulthood. Simson matriculated at the in 1701, intending to enter the Church. He followed the course in the faculty of arts (Latin, Greek, logic, natural phil ...[...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Point At Infinity
In geometry, a point at infinity or ideal point is an idealized limiting point at the "end" of each line. In the case of an affine plane (including the Euclidean plane), there is one ideal point for each pencil of parallel lines of the plane. Adjoining these points produces a projective plane, in which no point can be distinguished, if we "forget" which points were added. This holds for a geometry over any field, and more generally over any division ring. In the real case, a point at infinity completes a line into a topologically closed curve. In higher dimensions, all the points at infinity form a projective subspace of one dimension less than that of the whole projective space to which they belong. A point at infinity can also be added to the complex line (which may be thought of as the complex plane), thereby turning it into a closed surface known as the complex projective line, CP1, also called the Riemann sphere (when complex numbers are mapped to each point). In the c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Projectively Extended Real Line
In real analysis, the projectively extended real line (also called the one-point compactification of the real line), is the extension of the set of the real numbers, \mathbb, by a point denoted . It is thus the set \mathbb\cup\ with the standard arithmetic operations extended where possible, and is sometimes denoted by \mathbb^* or \widehat. The added point is called the point at infinity, because it is considered as a neighbour of both ends of the real line. More precisely, the point at infinity is the limit of every sequence of real numbers whose absolute values are increasing and unbounded. The projectively extended real line may be identified with a real projective line in which three points have been assigned the specific values , and . The projectively extended real number line is distinct from the affinely extended real number line, in which and are distinct. Dividing by zero Unlike most mathematical models of numbers, this structure allows division by zero: : ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dimensionless Quantity
Dimensionless quantities, or quantities of dimension one, are quantities implicitly defined in a manner that prevents their aggregation into unit of measurement, units of measurement. ISBN 978-92-822-2272-0. Typically expressed as ratios that align with another system, these quantities do not necessitate explicitly defined Unit of measurement, units. For instance, alcohol by volume (ABV) represents a volumetric ratio; its value remains independent of the specific Unit of volume, units of volume used, such as in milliliters per milliliter (mL/mL). The 1, number one is recognized as a dimensionless Base unit of measurement, base quantity. Radians serve as dimensionless units for Angle, angular measurements, derived from the universal ratio of 2π times the radius of a circle being equal to its circumference. Dimensionless quantities play a crucial role serving as parameters in differential equations in various technical disciplines. In calculus, concepts like the unitless ratios ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Affine Line
In mathematics, an affine space is a geometric structure that generalizes some of the properties of Euclidean spaces in such a way that these are independent of the concepts of distance and measure of angles, keeping only the properties related to parallelism and ratio of lengths for parallel line segments. Affine space is the setting for affine geometry. As in Euclidean space, the fundamental objects in an affine space are called ''points'', which can be thought of as locations in the space without any size or shape: zero-dimensional. Through any pair of points an infinite straight line can be drawn, a one-dimensional set of points; through any three points that are not collinear, a two-dimensional plane can be drawn; and, in general, through points in general position, a -dimensional flat or affine subspace can be drawn. Affine space is characterized by a notion of pairs of parallel lines that lie within the same plane but never meet each-other (non-parallel lines within ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cornell University
Cornell University is a Private university, private Ivy League research university based in Ithaca, New York, United States. The university was co-founded by American philanthropist Ezra Cornell and historian and educator Andrew Dickson White in 1865. Since its founding, Cornell University has been a Mixed-sex education, co-educational and nonsectarian institution. As of fall 2024, the student body included 16,128 undergraduate and 10,665 graduate students from all 50 U.S. states and 130 countries. The university is organized into eight Undergraduate education, undergraduate colleges and seven Postgraduate education, graduate divisions on its main Ithaca campus. Each college and academic division has near autonomy in defining its respective admission standards and academic curriculum. In addition to its primary campus in Ithaca, Cornell University administers three satellite campuses, including two in New York City, the Weill Cornell Medicine, medical school and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
William Kingdon Clifford
William Kingdon Clifford (4 May 18453 March 1879) was a British mathematician and philosopher. Building on the work of Hermann Grassmann, he introduced what is now termed geometric algebra, a special case of the Clifford algebra named in his honour. The operations of geometric algebra have the effect of mirroring, rotating, translating, and mapping the geometric objects that are being modelled to new positions. Clifford algebras in general and geometric algebra in particular have been of ever increasing importance to mathematical physics, geometry, and computing. Clifford was the first to suggest that gravitation might be a manifestation of an underlying geometry. In his philosophical writings he coined the expression ''mind-stuff''. Biography Born in Exeter, William Clifford was educated at Doctor Templeton's Academy on Bedford Circus and showed great promise at school. He went on to King's College London (at age 15) and Trinity College, Cambridge, where he was elected fello ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Allyn And Bacon
Allyn & Bacon, founded in 1868, is a higher education textbook publisher in the areas of education, humanities and social sciences. It is an imprint of Pearson Education, the world's largest education publishing and technology company, which is part of Pearson PLC. Allyn & Bacon was an independent company until it was purchased by Esquire, Inc., the former publishers of the magazine of the same name, in 1981. Esquire, Inc. was sold to Gulf+Western in 1983, and Allyn & Bacon became part of Simon & Schuster Simon & Schuster LLC (, ) is an American publishing house owned by Kohlberg Kravis Roberts since 2023. It was founded in New York City in 1924, by Richard L. Simon and M. Lincoln Schuster. Along with Penguin Random House, Hachette Book Group US ...'s education division. Pearson purchased the education and reference divisions of Simon & Schuster in 1998. In 2007, Allyn & Bacon merged with Merrill, also a Pearson company. As a result of the merge, the company's website c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Howard Eves
Howard Whitley Eves (10 January 1911, 6 June 2004) was an American mathematician, known for his work in geometry and the history of mathematics. Eves received his B.S. from the University of Virginia, an M.A. from Harvard University, and a Ph.D. in mathematics from Oregon State University in 1948, the last with a dissertation titled ''A Class of Projective Space Curves'' written under Ingomar Hostetter. He then spent most of his career at the University of Maine, 1954–1976. In later life, he occasionally taught at University of Central Florida. Eves was a strong spokesman for the Mathematical Association of America, which he joined in 1942, and whose Northeast Section he founded. For 25 years he edited the Elementary Problems section of the ''American Mathematical Monthly''. He solved over 300 problems proposed in various mathematical journals. His six volume ''Mathematical Circles'' series, collecting humorous and interesting anecdotes about mathematicians, was recently re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Karl Von Staudt
Karl Georg Christian von Staudt (24 January 1798 – 1 June 1867) was a German mathematician who used synthetic geometry to provide a foundation for arithmetic. Life and influence Karl was born in the Free Imperial City of Rothenburg, which is now called Rothenburg ob der Tauber in Germany. From 1814 he studied in Gymnasium in Ausbach. He attended the University of Göttingen from 1818 to 1822 where he studied with Gauss who was director of the observatory. Staudt provided an ephemeris for the orbits of Mars and the asteroid Pallas. When in 1821 Comet Nicollet-Pons was observed, he provided the elements of its orbit. These accomplishments in astronomy earned him his doctorate from University of Erlangen in 1822. Staudt's professional career began as a secondary school instructor in Würzburg until 1827 and then Nuremberg until 1835. He married Jeanette Dreschler in 1832. They had a son Eduard and daughter Mathilda, but Jeanette died in 1848. The book ''Geometrie der Lage'' (184 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Projective Harmonic Conjugate
In projective geometry, the harmonic conjugate point of a point on the real projective line with respect to two other points is defined by the following construction: :Given three collinear points , let be a point not lying on their join and let any line through meet at respectively. If and meet at , and meets at , then is called the harmonic conjugate of with respect to and . The point does not depend on what point is taken initially, nor upon what line through is used to find and . This fact follows from Desargues theorem. In real projective geometry, harmonic conjugacy can also be defined in terms of the cross-ratio as . Cross-ratio criterion The four points are sometimes called a harmonic range (on the real projective line) as it is found that always divides the segment ''internally'' in the same proportion as divides ''externally''. That is: \overline:\overline = \overline:\overline \, . If these segments are now endowed with the ordinary metri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
