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Angle Bisection with Straightedge and Compass
ANGLE BISECTION WITH STRAIGHTEDGE AND COMPASS The discussion below is largely based upon material and drawings from the following site : http://strader.cehd.tamu.edu/geometry/bisectangle1.0/bisectangle.html Angle Bisection Problem: To construct the angle bisector of an angle using an unmarked straightedge and collapsible compass . Given an angle to bisect ; for example , take ∠∠∠ ABC. To construct a point X in the interior of the angle such that the ray [BX bisects the angle . In other words , |∠∠∠ ABX| = |∠∠∠ XBC|. Step 1. Draw a circle that is centered at the vertex B of the angle . This circle can have a radius of any length, and it must intersect both sides of the angle . We shall call these intersection points P and Q. This provides a point on each line that is an equal distance from the vertex of the angle . Step 2. Draw two more circles . The first will be centered at P and will pass through Q, while the other will be centered at Q and pass through P. A basic continuity result in geometry implies that the two circles meet in a pair of points , one on each side of the line PQ (see the footnote at the end of this document). Take X to be the intersection point which is not on the same side of PQ as B. Equivalently , choose X so that X and B lie on opposite sides of PQ. Step 3. Draw a line through the vertex B and the constructed point X. We claim that the ray [BX will be the angle bisector . -
Vectors, Matrices and Coordinate Transformations
S. Widnall 16.07 Dynamics Fall 2009 Lecture notes based on J. Peraire Version 2.0 Lecture L3 - Vectors, Matrices and Coordinate Transformations By using vectors and defining appropriate operations between them, physical laws can often be written in a simple form. Since we will making extensive use of vectors in Dynamics, we will summarize some of their important properties. Vectors For our purposes we will think of a vector as a mathematical representation of a physical entity which has both magnitude and direction in a 3D space. Examples of physical vectors are forces, moments, and velocities. Geometrically, a vector can be represented as arrows. The length of the arrow represents its magnitude. Unless indicated otherwise, we shall assume that parallel translation does not change a vector, and we shall call the vectors satisfying this property, free vectors. Thus, two vectors are equal if and only if they are parallel, point in the same direction, and have equal length. Vectors are usually typed in boldface and scalar quantities appear in lightface italic type, e.g. the vector quantity A has magnitude, or modulus, A = |A|. In handwritten text, vectors are often expressed using the −→ arrow, or underbar notation, e.g. A , A. Vector Algebra Here, we introduce a few useful operations which are defined for free vectors. Multiplication by a scalar If we multiply a vector A by a scalar α, the result is a vector B = αA, which has magnitude B = |α|A. The vector B, is parallel to A and points in the same direction if α > 0. -
A Centennial Celebration of Two Great Scholars: Heiberg's
A Centennial Celebration of Two Great Scholars: Heiberg’s Translation of the Lost Palimpsest of Archimedes—1907 Heath’s Publication on Euclid’s Elements—1908 Shirley B. Gray he 1998 auction of the “lost” palimp- tains four illuminated sest of Archimedes, followed by col- plates, presumably of laborative work centered at the Walters Matthew, Mark, Luke, Art Museum, the palimpsest’s newest and John. caretaker, remind Notices readers of Heiberg was emi- Tthe herculean contributions of two great classical nently qualified for scholars. Working one century ago, Johan Ludvig support from a foun- Heiberg and Sir Thomas Little Heath were busily dation. His stature as a engaged in virtually “running the table” of great scholar in the interna- mathematics bequeathed from antiquity. Only tional community was World War I and a depleted supply of manuscripts such that the University forced them to take a break. In 2008 we as math- of Oxford had awarded ematicians should honor their watershed efforts to him an honorary doc- make the cornerstones of our discipline available Johan Ludvig Heiberg. torate of literature in Photo courtesy of to even mathematically challenged readers. The Danish Royal Society. 1904. His background in languages and his pub- Heiberg lications were impressive. His first language was In 1906 the Carlsberg Foundation awarded 300 Danish but he frequently published in German. kroner to Johan Ludvig Heiberg (1854–1928), a He had publications in Latin as well as Arabic. But classical philologist at the University of Copenha- his true passion was classical Greek. In his first gen, to journey to Constantinople (present day Is- position as a schoolmaster and principal, Heiberg tanbul) to investigate a palimpsest that previously insisted that his students learn Greek and Greek had been in the library of the Metochion, i.e., the mathematics—in Greek. -
Chapter Two Democritus and the Different Limits to Divisibility
CHAPTER TWO DEMOCRITUS AND THE DIFFERENT LIMITS TO DIVISIBILITY § 0. Introduction In the previous chapter I tried to give an extensive analysis of the reasoning in and behind the first arguments in the history of philosophy in which problems of continuity and infinite divisibility emerged. The impact of these arguments must have been enormous. Designed to show that rationally speaking one was better off with an Eleatic universe without plurality and without motion, Zeno’s paradoxes were a challenge to everyone who wanted to salvage at least those two basic features of the world of common sense. On the other hand, sceptics, for whatever reason weary of common sense, could employ Zeno-style arguments to keep up the pressure. The most notable representative of the latter group is Gorgias, who in his book On not-being or On nature referred to ‘Zeno’s argument’, presumably in a demonstration that what is without body and does not have parts, is not. It is possible that this followed an earlier argument of his that whatever is one, must be without body.1 We recognize here what Aristotle calls Zeno’s principle, that what does not have bulk or size, is not. Also in the following we meet familiar Zenonian themes: Further, if it moves and shifts [as] one, what is, is divided, not being continuous, and there [it is] not something. Hence, if it moves everywhere, it is divided everywhere. But if that is the case, then everywhere it is not. For it is there deprived of being, he says, where it is divided, instead of ‘void’ using ‘being divided’.2 Gorgias is talking here about the situation that there is motion within what is. -
On the Standard Lengths of Angle Bisectors and the Angle Bisector Theorem
Global Journal of Advanced Research on Classical and Modern Geometries ISSN: 2284-5569, pp.15-27 ON THE STANDARD LENGTHS OF ANGLE BISECTORS AND THE ANGLE BISECTOR THEOREM G.W INDIKA SHAMEERA AMARASINGHE ABSTRACT. In this paper the author unveils several alternative proofs for the standard lengths of Angle Bisectors and Angle Bisector Theorem in any triangle, along with some new useful derivatives of them. 2010 Mathematical Subject Classification: 97G40 Keywords and phrases: Angle Bisector theorem, Parallel lines, Pythagoras Theorem, Similar triangles. 1. INTRODUCTION In this paper the author introduces alternative proofs for the standard length of An- gle Bisectors and the Angle Bisector Theorem in classical Euclidean Plane Geometry, on a concise elementary format while promoting the significance of them by acquainting some prominent generalized side length ratios within any two distinct triangles existed with some certain correlations of their corresponding angles, as new lemmas. Within this paper 8 new alternative proofs are exposed by the author on the angle bisection, 3 new proofs each for the lengths of the Angle Bisectors by various perspectives with also 5 new proofs for the Angle Bisector Theorem. 1.1. The Standard Length of the Angle Bisector Date: 1 February 2012 . 15 G.W Indika Shameera Amarasinghe The length of the angle bisector of a standard triangle such as AD in figure 1.1 is AD2 = AB · AC − BD · DC, or AD2 = bc 1 − (a2/(b + c)2) according to the standard notation of a triangle as it was initially proved by an extension of the angle bisector up to the circumcircle of the triangle. -
The Dot Product
The Dot Product In this section, we will now concentrate on the vector operation called the dot product. The dot product of two vectors will produce a scalar instead of a vector as in the other operations that we examined in the previous section. The dot product is equal to the sum of the product of the horizontal components and the product of the vertical components. If v = a1 i + b1 j and w = a2 i + b2 j are vectors then their dot product is given by: v · w = a1 a2 + b1 b2 Properties of the Dot Product If u, v, and w are vectors and c is a scalar then: u · v = v · u u · (v + w) = u · v + u · w 0 · v = 0 v · v = || v || 2 (cu) · v = c(u · v) = u · (cv) Example 1: If v = 5i + 2j and w = 3i – 7j then find v · w. Solution: v · w = a1 a2 + b1 b2 v · w = (5)(3) + (2)(-7) v · w = 15 – 14 v · w = 1 Example 2: If u = –i + 3j, v = 7i – 4j and w = 2i + j then find (3u) · (v + w). Solution: Find 3u 3u = 3(–i + 3j) 3u = –3i + 9j Find v + w v + w = (7i – 4j) + (2i + j) v + w = (7 + 2) i + (–4 + 1) j v + w = 9i – 3j Example 2 (Continued): Find the dot product between (3u) and (v + w) (3u) · (v + w) = (–3i + 9j) · (9i – 3j) (3u) · (v + w) = (–3)(9) + (9)(-3) (3u) · (v + w) = –27 – 27 (3u) · (v + w) = –54 An alternate formula for the dot product is available by using the angle between the two vectors. -
Survey of Modern Mathematical Topics Inspired by History of Mathematics
Survey of Modern Mathematical Topics inspired by History of Mathematics Paul L. Bailey Department of Mathematics, Southern Arkansas University E-mail address: [email protected] Date: January 21, 2009 i Contents Preface vii Chapter I. Bases 1 1. Introduction 1 2. Integer Expansion Algorithm 2 3. Radix Expansion Algorithm 3 4. Rational Expansion Property 4 5. Regular Numbers 5 6. Problems 6 Chapter II. Constructibility 7 1. Construction with Straight-Edge and Compass 7 2. Construction of Points in a Plane 7 3. Standard Constructions 8 4. Transference of Distance 9 5. The Three Greek Problems 9 6. Construction of Squares 9 7. Construction of Angles 10 8. Construction of Points in Space 10 9. Construction of Real Numbers 11 10. Hippocrates Quadrature of the Lune 14 11. Construction of Regular Polygons 16 12. Problems 18 Chapter III. The Golden Section 19 1. The Golden Section 19 2. Recreational Appearances of the Golden Ratio 20 3. Construction of the Golden Section 21 4. The Golden Rectangle 21 5. The Golden Triangle 22 6. Construction of a Regular Pentagon 23 7. The Golden Pentagram 24 8. Incommensurability 25 9. Regular Solids 26 10. Construction of the Regular Solids 27 11. Problems 29 Chapter IV. The Euclidean Algorithm 31 1. Induction and the Well-Ordering Principle 31 2. Division Algorithm 32 iii iv CONTENTS 3. Euclidean Algorithm 33 4. Fundamental Theorem of Arithmetic 35 5. Infinitude of Primes 36 6. Problems 36 Chapter V. Archimedes on Circles and Spheres 37 1. Precursors of Archimedes 37 2. Results from Euclid 38 3. Measurement of a Circle 39 4. -
Math 3010 § 1. Treibergs First Midterm Exam Name
Math 3010 x 1. First Midterm Exam Name: Solutions Treibergs February 7, 2018 1. For each location, fill in the corresponding map letter. For each mathematician, fill in their principal location by number, and dates and mathematical contribution by letter. Mathematician Location Dates Contribution Archimedes 5 e β Euclid 1 d δ Plato 2 c ζ Pythagoras 3 b γ Thales 4 a α Locations Dates Contributions 1. Alexandria E a. 624{547 bc α. Advocated the deductive method. First man to have a theorem attributed to him. 2. Athens D b. 580{497 bc β. Discovered theorems using mechanical intuition for which he later provided rigorous proofs. 3. Croton A c. 427{346 bc γ. Explained musical harmony in terms of whole number ratios. Found that some lengths are irrational. 4. Miletus D d. 330{270 bc δ. His books set the standard for mathematical rigor until the 19th century. 5. Syracuse B e. 287{212 bc ζ. Theorems require sound definitions and proofs. The line and the circle are the purest elements of geometry. 1 2. Use the Euclidean algorithm to find the greatest common divisor of 168 and 198. Find two integers x and y so that gcd(198; 168) = 198x + 168y: Give another example of a Diophantine equation. What property does it have to be called Diophantine? (Saying that it was invented by Diophantus gets zero points!) 198 = 1 · 168 + 30 168 = 5 · 30 + 18 30 = 1 · 18 + 12 18 = 1 · 12 + 6 12 = 3 · 6 + 0 So gcd(198; 168) = 6. 6 = 18 − 12 = 18 − (30 − 18) = 2 · 18 − 30 = 2 · (168 − 5 · 30) − 30 = 2 · 168 − 11 · 30 = 2 · 168 − 11 · (198 − 168) = 13 · 168 − 11 · 198 Thus x = −11 and y = 13 . -
Thales of Miletus Sources and Interpretations Miletli Thales Kaynaklar Ve Yorumlar
Thales of Miletus Sources and Interpretations Miletli Thales Kaynaklar ve Yorumlar David Pierce October , Matematics Department Mimar Sinan Fine Arts University Istanbul http://mat.msgsu.edu.tr/~dpierce/ Preface Here are notes of what I have been able to find or figure out about Thales of Miletus. They may be useful for anybody interested in Thales. They are not an essay, though they may lead to one. I focus mainly on the ancient sources that we have, and on the mathematics of Thales. I began this work in preparation to give one of several - minute talks at the Thales Meeting (Thales Buluşması) at the ruins of Miletus, now Milet, September , . The talks were in Turkish; the audience were from the general popu- lation. I chose for my title “Thales as the originator of the concept of proof” (Kanıt kavramının öncüsü olarak Thales). An English draft is in an appendix. The Thales Meeting was arranged by the Tourism Research Society (Turizm Araştırmaları Derneği, TURAD) and the office of the mayor of Didim. Part of Aydın province, the district of Didim encompasses the ancient cities of Priene and Miletus, along with the temple of Didyma. The temple was linked to Miletus, and Herodotus refers to it under the name of the family of priests, the Branchidae. I first visited Priene, Didyma, and Miletus in , when teaching at the Nesin Mathematics Village in Şirince, Selçuk, İzmir. The district of Selçuk contains also the ruins of Eph- esus, home town of Heraclitus. In , I drafted my Miletus talk in the Math Village. Since then, I have edited and added to these notes. -
CSU200 Discrete Structures Professor Fell Integers and Division
CSU200 Discrete Structures Professor Fell Integers and Division Though you probably learned about integers and division back in fourth grade, we need formal definitions and theorems to describe the algorithms we use and to very that they are correct, in general. If a and b are integers, a ¹ 0, we say a divides b if there is an integer c such that b = ac. a is a factor of b. a | b means a divides b. a | b mean a does not divide b. Theorem 1: Let a, b, and c be integers, then 1. if a | b and a | c then a | (b + c) 2. if a | b then a | bc for all integers, c 3. if a | b and b | c then a | c. Proof: Here is a proof of 1. Try to prove the others yourself. Assume a, b, and c be integers and that a | b and a | c. From the definition of divides, there must be integers m and n such that: b = ma and c = na. Then, adding equals to equals, we have b + c = ma + na. By the distributive law and commutativity, b + c = (m + n)a. By closure of addition, m + n is an integer so, by the definition of divides, a | (b + c). Q.E.D. Corollary: If a, b, and c are integers such that a | b and a | c then a | (mb + nc) for all integers m and n. Primes A positive integer p > 1 is called prime if the only positive factor of p are 1 and p. -
Lecture 4. Pythagoras' Theorem and the Pythagoreans
Lecture 4. Pythagoras' Theorem and the Pythagoreans Figure 4.1 Pythagoras was born on the Island of Samos Pythagoras Pythagoras (born between 580 and 572 B.C., died about 497 B.C.) was born on the island of Samos, just off the coast of Asia Minor1. He was the earliest important philosopher who made important contributions in mathematics, astronomy, and the theory of music. Pythagoras is credited with introduction the words \philosophy," meaning love of wis- dom, and \mathematics" - the learned disciplines.2 Pythagoras is famous for establishing the theorem under his name: Pythagoras' theorem, which is well known to every educated per- son. Pythagoras' theorem was known to the Babylonians 1000 years earlier but Pythagoras may have been the first to prove it. Pythagoras did spend some time with Thales in Miletus. Probably by the suggestion of Thales, Pythagoras traveled to other places, including Egypt and Babylon, where he may have learned some mathematics. He eventually settled in Groton, a Greek settlement in southern Italy. In fact, he spent most of his life in the Greek colonies in Sicily and 1Asia Minor is a region of Western Asia, comprising most of the modern Republic of Turkey. 2Is God a mathematician ? Mario Livio, Simon & Schuster Paperbacks, New York-London-Toronto- Sydney, 2010, p. 15. 23 southern Italy. In Groton, he founded a religious, scientific, and philosophical organization. It was a formal school, in some sense a brotherhood, and in some sense a monastery. In that organization, membership was limited and very secretive; members learned from leaders and received education in religion. -
Basics of Linear Algebra
Basics of Linear Algebra Jos and Sophia Vectors ● Linear Algebra Definition: A list of numbers with a magnitude and a direction. ○ Magnitude: a = [4,3] |a| =sqrt(4^2+3^2)= 5 ○ Direction: angle vector points ● Computer Science Definition: A list of numbers. ○ Example: Heights = [60, 68, 72, 67] Dot Product of Vectors Formula: a · b = |a| × |b| × cos(θ) ● Definition: Multiplication of two vectors which results in a scalar value ● In the diagram: ○ |a| is the magnitude (length) of vector a ○ |b| is the magnitude of vector b ○ Θ is the angle between a and b Matrix ● Definition: ● Matrix elements: ● a)Matrix is an arrangement of numbers into rows and columns. ● b) A matrix is an m × n array of scalars from a given field F. The individual values in the matrix are called entries. ● Matrix dimensions: the number of rows and columns of the matrix, in that order. Multiplication of Matrices ● The multiplication of two matrices ● Result matrix dimensions ○ Notation: (Row, Column) ○ Columns of the 1st matrix must equal the rows of the 2nd matrix ○ Result matrix is equal to the number of (1, 2, 3) • (7, 9, 11) = 1×7 +2×9 + 3×11 rows in 1st matrix and the number of = 58 columns in the 2nd matrix ○ Ex. 3 x 4 ॱ 5 x 3 ■ Dot product does not work ○ Ex. 5 x 3 ॱ 3 x 4 ■ Dot product does work ■ Result: 5 x 4 Dot Product Application ● Application: Ray tracing program ○ Quickly create an image with lower quality ○ “Refinement rendering pass” occurs ■ Removes the jagged edges ○ Dot product used to calculate ■ Intersection between a ray and a sphere ■ Measure the length to the intersection points ● Application: Forward Propagation ○ Input matrix * weighted matrix = prediction matrix http://immersivemath.com/ila/ch03_dotprodu ct/ch03.html#fig_dp_ray_tracer Projections One important use of dot products is in projections.