What is Geometric: Definition and 808 Discussions

Geometry (from the Ancient Greek: γεωμετρία; geo- "earth", -metron "measurement") is, with arithmetic, one of the oldest branches of mathematics. It is concerned with properties of space that are related with distance, shape, size, and relative position of figures. A mathematician who works in the field of geometry is called a geometer.
Until the 19th century, geometry was almost exclusively devoted to Euclidean geometry, which includes the notions of point, line, plane, distance, angle, surface, and curve, as fundamental concepts.During the 19th century several discoveries enlarged dramatically the scope of geometry. One of the oldest such discoveries is Gauss' Theorema Egregium ("remarkable theorem") that asserts roughly that the Gaussian curvature of a surface is independent from any specific embedding in an Euclidean space. This implies that surfaces can be studied intrinsically, that is as stand alone spaces, and has been expanded into the theory of manifolds and Riemannian geometry.
Later in the 19th century, it appeared that geometries without the parallel postulate (non-Euclidean geometries) can be developed without introducing any contradiction. The geometry that underlies general relativity is a famous application of non-Euclidean geometry.
Since then, the scope of geometry has been greatly expanded, and the field has been split in many subfields that depend on the underlying methods—differential geometry, algebraic geometry, computational geometry, algebraic topology, discrete geometry (also known as combinatorial geometry), etc.—or on the properties of Euclidean spaces that are disregarded—projective geometry that consider only alignment of points but not distance and parallelism, affine geometry that omits the concept of angle and distance, finite geometry that omits continuity, etc.
Originally developed to model the physical world, geometry has applications in almost all sciences, and also in art, architecture, and other activities that are related to graphics. Geometry also has applications in areas of mathematics that are apparently unrelated. For example, methods of algebraic geometry are fundamental in Wiles's proof of Fermat's Last Theorem, a problem that was stated in terms of elementary arithmetic, and remained unsolved for several centuries.

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  1. T

    Geometric sequence, determining the value of the first term

    question - if the 3rd and 9th term of a geometric series with a positive common ratio are -3 and -192 respectively, determine the value fo the first term, a. I kno we using a_n=a_1r^n-1 From that i got this : -3 = a_1r^2 -192 = a_1r^8 But I don't kno how I can solve for r or...
  2. P

    Understanding the Geometric Meaning of Gradient through its Definition

    Consider a function of two variable x,y , is it possible to understand the geometric meaning of the gradient just by looking its definition \nabla f = \frac{\partial f}{\partial x} \hat{x} + \frac{\partial f}{\partial y} \hat{y} I can understand the geometric meaning by directional...
  3. N

    Geometric power series of f(x)=6/(2-x) c=1

    Find the geometric power series for the given function: f(x)=6/(2-x) c=1 I am stumped on this one. I've tried for an hour on this one with no luck. Could someone help?
  4. M

    Geometric progression, is this correct? ratio/first/next term

    Hello everyone, I'm trying to solve the following: If n is an integer and n > = 1, find a formula for the expression 2^n - 2^{n-1} + 2^{n-2} - 2^{n-3} + ... + (-1)^{n-1} * 2 + (-1)^n okay this confuses me, because I'm not sure which is the first term and which is the last term... I...
  5. F

    Geometric Power Series Representation of ln(1+2x) at c=0

    I was wondering if someone could check my work: Find the geometric power series representation of f(x)=ln(1+2x), c=0 I get \\sum_{n=0}^ \\infty2(-2x)^n+1 on -1/2<x<1/2
  6. M

    Geometric progressions, i seem to be messing up on simple algebra

    hello everyone, I'm trying to figure out this geometric progession and I'm checking it with my calculator and I'm definatley not getting what they are getting: I'm trying to find the term after the last term, I found the ratio which is 3/2, now I must multiply that ratio by the last term...
  7. M

    How to Simplify (11-1)^9 Using Binomial Expansion?

    Hello everyone. I'm studying for my exam and I'm reveiwing some problems but this one isn't making sense to me: 11^9(9 choose 0) - 11^8(9 choose 1) + 11^7(9 choose 2) - ... - 11^2(9 choose 7) + 11^1 (9 choose 8) - 11^0 (9 choose 9) answer: (11-1)^9 = 10^9 = 1,000,000,000. work...
  8. M

    Help Needed: Geometric Progression & Arithmetic Sums

    Hello everyone I'm studying for my next exam and I screwed up on the geometric progressions and arthm and they are the easiest of them all but I don't know what I'm doing wrong. The first problem on the exam said: Suppose that an arithmetic series has 202 terms. If the first term is 4PI and...
  9. G

    Find First Term and Common Ratio of Geometric Progression | Step-by-Step Guide

    ok, the qn goes like this.. Find the first term and common ration of a geometric progression if the sum to n is given by 6 - 2/(3^(n-1)) I tried solving by making both terms of the eqn having the same denominator by multiplying (3^(n-1)) to the first term 6 and then by taking out the 2...
  10. MathematicalPhysicist

    Geometric Topology Vs. Algebraic Topology.

    i know that geometric topology is a field that is connected to knot theory, i wonder what are the similarities between the two subjects, and in what subject in particular they overlap?
  11. H

    Geometric and Physical Interpretation of Diagonalization

    I am a second year student in quantum mechanics. I heard in lecture that simultaneous diagonalization of matrices is important in quantum mechanics. I would like to know why is it significant when two matrices can be simultaneous diagonalized, and what is the geometric and physical...
  12. L

    Why Does Geometric Sequence General Term Formula Use n, Not n-1?

    do you have an explanation to why sometimes the general term formula for geometric sequence is not raised to n-1 but to simply n?
  13. T

    Can a sequence be arithmatic and geometric?

    can a sequence be arithmatic and geometric?? can a sequence be arithmatic an geometric??
  14. E

    Deriving a geometric series

    I could use some help with this question: Derive the geometric series representation of 1/(1-x) by finding a0, a1, a2,... such that (1-x)(a0+a1x+a2x^2+a3X^3+...)=1 Thank you.
  15. S

    Matrix geometric representation

    Hello all, I have attached a matrix. I am trying to work out this matrix will transform a set of co-ordinates (x_1, y_1, z_1) to a new set of co-ordinates (x_2, y_2, z_2) Can anyone give me any hints on how to tackle this problem?
  16. M

    Summing Geometric Sequences am i doing this right?

    We learned in class how to find the sum of any geometric sequence with the following formula: Let x = Sum Of Geometric Sequence; x = [Take mythical next term - real term]/(ratio - 1); The real term is the first term of the sequence and the mythical next term would be the next term for...
  17. N

    Need help understanding wording of simple geometric optics problem

    I understand the material this problem is based on very well, but I feel very sad when I read this problem because it makes very little sense to me. I'm hoping it's just me that's confused by it and not everyone else - because in that case I should be able to get help here. Here is the...
  18. L

    What is the difference between structural isomerism and geometric isomerism?

    What is the difference between structural isomerism and geometric isomerism?? Yea. The thread title explains it.
  19. P

    Geometric Optics- Two Questions

    1.Determine the magnification of a 5cm object that has been placed 20 cm in front of a lens with a power of -2.5 d? 2. Light strikes a rectangular piece of crown glass with an angle of incidence of 30 degrees. If the block of glass is 10cm, determine the measure of lateral displacement. Can...
  20. V

    Geometric interpetation of a complex number in R^2

    For this problem i am given two complex numbers Z_1 , Z_2 and then a third which is the sum of the first two complex numbers Z_3 . I am then asked to find the geometric interpetation of these numbers in \mathbb{R}^2 . I am fine when graphing them in the complex plane but unsure of what they...
  21. P

    Geometric optics vs Electromagnetic waves

    Light which are electromagnetic waves have an electric field component and magnetic field component. The electric field can be phase shifted but the magnetic field never does. In geometric optics, light is modeled as a straight line and its rules upon reflection and refraction are according...
  22. Oxymoron

    Can Every Combinatorial Graph Be Proven to Correspond to a Topological Space?

    I've read (and I've been told in lectures) that each graph (let's just say a combinatorial graph) corresponds to a topological space called the geometric realization - in this space the vertices are distinct points and the edges are subspaces homeomorphic to [0,1]. My question is this: Is this...
  23. A

    Proving geometric theorems by vector method

    I am learning vectors in which there is a section in which geometric theorems are proved with the help of vectors. However while solving problems I often face difficulty on how to proceed ,where to use dot product, cross and etc.Is there any systematic manner on how to prove these ? Please...
  24. E

    Infinity geometric series question

    Hi there everyone! Have a quick question for you. The question is: The sum to infinity of a geometric series is 9/2 The second term of the series is -2 Find the value of r, the common ratio of the series. I understand that we have to use the sum to infinity of a geometric series...
  25. W

    Things to expect with grade 10 Geometric Sequences

    We're going to be starting them in a day or two, and I just wanted to know ahead of time what you guys might think we'll be learning with them, like formulae and that kind of stuff..
  26. K

    Geometric Series: Summing the Powers of x

    Find the sum of the series: \sum\limits_{n = 1}^\infty {nx^n } if \left| x \right| < 1 I thought maybe with the geometric form, but I am not sure.
  27. M

    Is the Sum of a Geometric Series Always Equal to 2?

    Hi Folks, I have this here geometric series which I'm supposed to find the sum of: Given \sum_{n=0} ^{\infty} \frac{2n+1}{2^n} I the sum into sub-sums \sum_{n=0} ^{\infty} 2^{-n} + \sum_{n=0} ^{\infty} \frac{1}{2}^{n-1} taking 2^{-n} Since x^n converges towards 1/1+x therefore I...
  28. N

    Geometric deduction problem ?

    Please help me to solve the following question : ABCD is a parallelogram .BA is procude to X and BA=AX . Prove that angle of XCB is 90 degree.
  29. J

    What are the possible values of x in this geometric series?

    Hey guys i was having trouble on this question so i was wondering if someone could help me :) In a geometric series, (x-2),(x+5), and (4x-8) are consecutive terms. Determine all possible values of x. :confused:
  30. M

    Summing a Geometric Series: Can We Use the Formula 1/(1-x)?

    Hi Can I claim that in order to find the sum of the series: \sum_{n = 0} ^{\infty} 2^{- n} \sum_{n = 0} ^{\infty} 2^{- n} = \sum_{n = 0} ^{\infty} x^n = \frac{1}{1-x} ? Sincerely Yours Fred
  31. K

    Eigenblades and the Geometric Algebra of Spinors

    I've been looking into Geometric Algebra approaches to linear transformations and have found it to be MUCH nicer than the conventional matrix approaches for certain kinds of transformations. Moreover, I find it much more intuitive, particularly in its way of dealing with complex numbers. For...
  32. O

    Geometric Series Derivation for Given Identities

    I am trying to derive the geometric series for the following given identities, \begin{array}{l} \frac{1}{{0.99}} = 1.0101010101... \; \; \; {\rm{ (1)}} \\ \frac{1}{{0.98}} = 1.0204081632... \; \; \; {\rm{ (2)}} \\ \end{array} Here is my answer for (1), \sum\limits_{n = 1}^\infty...
  33. M

    Urgend Geometric series question

    Hi I have the following problem: show that 1/(1+x^2)) = 1-x^2 + x^4 + (-1)^n*(x^2n-2) + (-1)^n * (x^2n)/(1+x^2) I that know this arctan function can be expanded as a geometric series by using: 1 + q + q^2 + q^3 + ... + = 1/(1-q) Then by putting q = -x^2. I get...
  34. daniel_i_l

    A gravity graph is a kind of art "tool" that lets you draw nice geometric shapes

    A gravity graph is a kind of art "tool" that let's you draw nice geometric shapes. It has a board the size of a piece of paper that is weighted in the middle, each of the corners is connected to a piece of string and the strings are tied to a small rectangle (paralell to the board) about 1.5...
  35. P

    Geometric Interpretation Of Schrodinger's

    GEOMETRICAL STUDY OF SCHROEDINGER'S FORMULA If we take a look on previous expression, we could continue with the importance of complex numbers. The complex numbers are very important to represent points or vectors in plane, and can be expressed this way: a = b·x+c·y If we choose...
  36. R

    Geometric rotation of (a + bi)

    Question, in order to produce a 270 degree geometric rotation of the complex number (a + bi), would this be correct: (a + bi) * (-i) It seems logical since a 90 degree rotation results from (a + bi) * (i) Next question. What would be the equations for rotation of (a + bi) by 45 degrees, 135...
  37. T

    The Geometric Heat Equation-WTF?

    The Geometric Heat Equation--WTF?? I need some help getting from point A to B. Let's say we have the plain ol' heat equation u_t=\Delta u where the u=u\left(x,t\right), and that's all good. Then, we also have the so-called geometric heat equation \dfrac{\partial F}{\partial t}=kN where...
  38. CarlB

    A Geometric Approach to the Standard Model, Greg Trayling

    A Geometric Approach to the Standard Model Greg Trayling, Dept of Phys, U. Windsor, Windsor, Ontario A geometric approach to the standard model of the Clifford algebra \mathcal{CL}_7 is advanced. The gauge symmetries and charge assignments of the fundamental fermions are seen to arise from a...
  39. A

    Geometric derivations of distance

    aristarchus was the greek astronomer who was the first to find out the distance between the Earth and the sun. he observed that when the moon was exactly half full; the Earth (E), moon (M), and sun (S) formed a right triangle with the right angle at the moon. then how did he found out that the...
  40. benorin

    A Geometric Product (a series of exercises for the curious)

    I hope you have fun with these... OK, so you know the geometric series, right? It goes like this: \sum_{k=0}^{\infty} z^k = \frac{1}{1-z},\forall z\in\mathbb{C}\mbox{ such that }\left| z\right|<1 How about this one? Call it, say, the geometric product: \prod_{k=0}^{\infty} \left( 1+...
  41. B

    Verifying Geometric Series Formula: \sum\limits_{k = 0}^N {r^k }

    This has been bothering me for a while. I've seen many different versions of this and I'd just like to get the following cleared up. Is the following true? \sum\limits_{k = 0}^N {r^k } = \frac{{1 - r^{N + 1} }}{{1 - r}} There are other related things I am slightly worried about but I...
  42. P

    Geometric random variable with probability mass function

    If you have a geometric random variable with probability mass function: P(X=n) = p(1-p)^n n = 0,1,2,3... Find the Mean and the Variance. ---------------------------- Okay, I've looked everywhere and tried everything, however, i just cannot get it. i think that your supposed...
  43. S

    Geometric Significance of the Dihedral Group D/o

    Consider the dihedral group D/o, generated by x and y where o(x)=2 and o(y)=5 What is the geometric significance of D/o? Which of G/<x> and G/<y> are well defined groups? Give reasons?
  44. CarlB

    Hestenes' Geometric Algebra. What good is it?

    Why don't we discuss the Geometric algebra and how it differs from other Clifford algebras? For introduction, here's Hestenes' home page on Geometric calculus: http://modelingnts.la.asu.edu/ This is an easy reading introduction: (1) GA seamlessly integrates the properties of vectors...
  45. M

    Can Geometric Optics Help Solve These Light Refraction Problems?

    In my first two of weeks we covered most of the light unit, and i was sick(in class, but coulnd't focus or abosrb information) and now i am at the end of the unit with this due tomoro and i do not understand how to do any, I need to learn how to do this, I can't understand most of it right...
  46. D

    Geometric Proof of Dot Product: |A dot B| ≤ |A||B|

    I am doing a assingment for my classical mechanics class that requires the proof of: The dot product of |A dot B| <= (less than or equeal to) |A| |B| . I did the algebraic proof fine but we are required to do a geometic proof as well. This leaves me with the question what is the geometic...
  47. F

    Geometric proof for vector relation-

    geometric proof for vector relation-please help! hi there... i am trying to prove the following relation from vectors geometrically however nothing comes to my mind..i have succeeded in proving it algebraically. CAN ANYONE help me as to how do i prove this relation geometrically. The...
  48. E

    Solving Geometric Optics Problem: Raising Height of Camera

    Here's a question that everyone in my class that I talked to couldn't find an answer to. "Suppose that you focus a camera direclty down on a printed letter on this page. The letter is then covered with a 1.00mm thick microscope slide (n = 1.55). How high must the camera be raised in order to...
  49. D

    Is it possible to derive Lorentz-transforms through geometric methods?

    Has anyone derived the Lorentz-transforms by using 'simple' geometrics? If so, could I get a link for the paper please. I tried to google for one but couldn't find.
  50. U

    How many generations must a person go back to have at least 1000 ancestors?

    Hi everyone, I'm new to these forums, so I've only just realized how much help they can be... I have some questions so please, don't hesitate to aid me in my time of need. These are regarding geometric sequences and series. I'm supposed to be using S=a+ar^n/1-r where s=the sum of the...
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