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Geometrical Constructions in Dynamic and Interactive Mathematics Learning Environment
Mevlana International Journal of Education (MIJE) Vol. 3(3) INVITED ARTICLE Special Issue: Dynamic and Interactive Mathematics Learning Environment pp. 50- 63, 01 July, 2013 Available online at http://mije.mevlana.edu.tr/ http://dx.doi.org/10.13054/mije.si.2013.06 Geometrical Constructions in Dynamic and Interactive Mathematics Learning Environment Margo Kondratieva* Faculty of Education and Department of Mathematics and Statistics, Memorial University, St. John’s, Canada This paper concerns teaching Euclidean geometry at the university level. Article history It is based on the authors’ personal experience. It describes a sequence of learning activities that combine geometrical constructions with Received: 21 December 2012 explorations, observations, and explanations of facts related to the geometry of triangle. Within this approach, a discussion of the Euler and Received in revised form: Nigel lines receives a unified treatment via employment of a plane - transformation that maps a triangle into its medial triangle. I conclude Accepted: 17 May 2013 that during this course delivery, the role of constructions in dynamic and interactive environment was significant for students’ genuine Key words: understanding of the subject. In particular, it helped them to work with explorations; concrete figures and develop their own preformal approaches before geometrical learning general theorems and proofs. At the same time it was essential to constructions; proofs, follow such strategies as gradually lead students from basic to advanced basic geometric configurations, constructions, from making simple analogies to generalizations based on interconnectivity, plane critical ideas and unified principles, and emphasize structural transformation, Euler interconnectedness of the problems each of which adds a new element line, Nagel line. -
The New Proof of Euler's Inequality Using Spieker Center
of Math al em rn a u ti o c International Journal of Mathematics And its Applications J s l A a n n d o i i Volume 3, Issue 4{E (2015), 67{73. t t a s n A r e p t p ISSN: 2347-1557 n l I i c • a t 7 i o 5 n 5 • s Available Online: http://ijmaa.in/ 1 - 7 4 I 3 S 2 S : N International Journal of Mathematics And its Applications The New Proof of Euler's Inequality Using Spieker Center Research Article Dasari Naga Vijay Krishna1∗ 1 Department of Mathematics, Keshava Reddy Educational Instutions, Machiliaptnam, Kurnool, India. Abstract: If R is the Circumradius and r is the Inradius of a non-degenerate triangle then due to EULER we have an inequality referred as \Euler's Inequality"which states that R ≥ 2r, and the equality holds when the triangle is Equilateral. In this article let us prove this famous inequality using the idea of `Spieker Center '. Keywords: Euler's Inequality, Circumcenter, Incenter, Circumradius, Inradius, Cleaver, Spieker Center, Medial Triangle, Stewart's Theorem. c JS Publication. 1. Historical Notes [4] In 1767 Euler analyzed and solved the construction problem of a triangle with given orthocenter, circum center, and in center. The collinearlity of the Centroid with the orthocenter and circum center emerged from this analysis, together with the celebrated formula establishing the distance between the circum center and the in center of the triangle. The distance d between the circum center and in center of a triangle is given by d2 = R(R − 2r) where R, r are the circum radius and in radius, respectively. -
A Short Proof of EULER's INEQUILITY Using SPIEKER CENTER
A short Proof of EULER’S INEQUILITY using SPIEKER CENTER Dasari Naga Vijay Krishna Department of Mathematics, Keshava Reddy Educational Intuitions Machiliaptnam, Kurnool, INDIA E-mail: [email protected] Abstract: If R is the Circum Radius and r is the in Radius of a non-degenerate triangle then due to EULER we have an inequality referred as “Euler’s Inequality” which states that R ≥ 2r, and the equality holds when the triangle is Equilateral. In this article let us prove this famous inequality using the idea of Spieker Center. Keywords: Euler’s Inequality, Circum Center, In Center, Circum Radius, In Radius, Cleaver, Spieker Center, Medial Triangle, Stewart’s Theorem. Historical Notes In 1767 Euler analyzed and solved the construction problem of a triangle with given orthocenter, circum center, and in center. The collinearity of the Centroid with the orthocenter and circum center emerged from this analysis, together with the celebrated formula establishing the distance between the circum center and the in center of the triangle. The distance d between the circum center and in center of a triangle is given by = R(R-2r), where R, r will be the circum radius and in radius, respectively. This formula often called as Euler’s triangle formula. An immediate consequence of this theorem is ≥ 2r, which is often referred as Euler’s triangle inequality. According to Coxeter, although this inequality had been published by Euler in 1767, it had appeared earlier in 1746 in a publication by William Chapple. This ubiquitous inequality occurs in the literature in many different equivalent forms. For example, A B C 1 8Sin Sin Sin , 2 2 2 r r r 9r, a b c 25 abc a b cc a bb c a, x y y z z x 8xyz, Where a,b,c A,B,C, , , denote the sides, andles exradii of the triangle, and x, y, z are arbitrary nonnegative numbers such that a = y+z, b = x+z, c = x+y. -
Concurrent Lines Lines in a Plane Or Higher-Dimensional Space Are Said to Be Concurrent If They Intersect at a Single Point
Concurrent lines lines in a plane or higher-dimensional space are said to be concurrent if they intersect at a single point. Examples[edit] Triangles[edit] In a triangle, four basic types of sets of concurrent lines are altitudes, angle bisectors, medians, and perpendicular bisectors: A triangle's altitudes run from each vertex and meet the opposite side at a right angle. The point where the three altitudes meet is the orthocenter. Angle bisectors are rays running from each vertex of the triangle and bisecting the associated angle. They all meet at the incenter. Medians connect each vertex of a triangle to the midpoint of the opposite side. The three medians meet at the centroid. Perpendicular bisectors are lines running out of the midpoints of each side of a triangle at 90 degree angles. The three perpendicular bisectors meet at the circumcenter. Other sets of lines associated with a triangle are concurrent as well. For example: Any median (which is necessarily a bisector of the triangle's area) is concurrent with two other area bisectors each of which is parallel to a side.[1] A cleaver of a triangle is a line segment that bisects the perimeter of the triangle and has one endpoint at the midpoint of one of the three sides. The three cleavers concur at the center of the Spieker circle, which is the incircle of the medial triangle. A splitter of a triangle is a line segment having one endpoint at one of the three vertices of the triangle and bisecting the perimeter. The three splitters concur at the Nagel point of the triangle.