Linear algebra Definition and 999 Threads

Linear algebra is the branch of mathematics concerning linear equations such as:





a

1



x

1


+

+

a

n



x

n


=
b
,


{\displaystyle a_{1}x_{1}+\cdots +a_{n}x_{n}=b,}
linear maps such as:




(

x

1


,

,

x

n


)


a

1



x

1


+

+

a

n



x

n


,


{\displaystyle (x_{1},\ldots ,x_{n})\mapsto a_{1}x_{1}+\cdots +a_{n}x_{n},}
and their representations in vector spaces and through matrices.Linear algebra is central to almost all areas of mathematics. For instance, linear algebra is fundamental in modern presentations of geometry, including for defining basic objects such as lines, planes and rotations. Also, functional analysis, a branch of mathematical analysis, may be viewed as the application of linear algebra to spaces of functions.
Linear algebra is also used in most sciences and fields of engineering, because it allows modeling many natural phenomena, and computing efficiently with such models. For nonlinear systems, which cannot be modeled with linear algebra, it is often used for dealing with first-order approximations, using the fact that the differential of a multivariate function at a point is the linear map that best approximates the function near that point.

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  1. Q

    Can I Successfully Take Calc 3 and Linear Algebra at the Same Time?

    Hi all! I have an important decision to make for the summer of 2016 and I need some advice from some who have taken these courses. I need one biology lab elective to graduate, but it is a field lab and it runs from from 5/13 - 6/19. Because it is a field lab, I will not be able to take other...
  2. F

    Prove that three functions form a dual basis

    Homework Statement Homework Equations[/B] The Attempt at a Solution From that point, I don't know what to do. How do I prove linear independence if I have no numerical values? Thank you.
  3. P

    Linear algebra : Doing a proof with a square matrix

    Homework Statement Show that all square matrix (A whatever) can be written as the sum of a symmetric matrix and a anti symmetric matrix. Homework Equations I think this relation might be relevant : $$ A=\frac{1}{2}*(A+A^{T})+\frac{1}{2}*(A-A^{T}) $$ The Attempt at a Solution I know that we...
  4. C

    Understanding Matrices Sums and Products

    Homework Statement Suppose that AB = AC for matrices A, B, and C. Is it true that B must equal C? Prove the result or find a counterexample. Homework Equations Properties of matrix multiplication The Attempt at a Solution AC = A(D + B) = AD + AB = 0 + AB = AB ? Can someone help me...
  5. G

    Linear algebra: Find the matrix of linear transformation

    Homework Statement Check if L(p)(x)=(1+4x)p(x)+(x-x^2)p'(x)-(x^2+x^3)p''(x) is a linear transformation on \mathbb{R_2}[x]. If L(p)(x) is a linear transformation, find it's matrix in standard basis and check if L(p)(x) is invertible. If L(p)(x) is invertible, find the function rule of it's...
  6. C

    Matrix-Vector Form Write an Augmented Matrix

    Homework Statement Write in Vector-Matrix form then write the augmented matrix of the system. r + 2s + t = 1 r - 3s +3t = 1 4s - 5t = 3 Homework Equations The matrix to which the operations will be applied is called the augmented matrix of the system Ax = b, It is formed by appending the...
  7. G

    Linear algebra: Prove that the set is a subspace

    Homework Statement Let U is the set of all commuting matrices with matrix A= \begin{bmatrix} 2 & 0 & 1 \\ 0 & 1 & 1 \\ 3 & 0 & 4 \\ \end{bmatrix}. Prove that U is the subspace of \mathbb{M_{3\times 3}} (space of matrices 3\times 3). Check if it contains span\{I,A,A^2,...\}. Find the...
  8. Jianphys17

    Is there a generalized curl operator for dimensions higher than 3?

    Hi, i now studying vector calculus, and for sheer curiosity i would like know if there exist a direct fashion to generalize the rotor operator, to more than 3 dimensions! On wiki there exist a voice https://en.wikipedia.org/wiki/Curl_(mathematics)#Generalizations , but I do not know how you...
  9. R

    Failing a Class? Advice for Physics/Math Major

    Ok, so this is really weird. I am a second year physics major at a decent university. My GPA at the moment is not steller (3.3). I think I totally bombed my lower division linear algebra midterm, and I might (a big maybe, because I am confident that I could pass this class if I put my 110%...
  10. ahmed habala

    Hi all -- I need a good reference about linear algebra

    hi all i need a good Reference about mathematics my level in mathematics as zero
  11. P

    How can a matrix with no zero eigenvalues be used to combine solutions to PDEs?

    Homework Statement If you have the heat equation $$u_{t}-u_{xx}=a \\ u(0,t)=b\\u(1,t)=c\\u(x,0)=d$$ Show that the solution to the above equation can be made up of a linear combination of solutions to $$u_{t}-u_{xx}=a_i \\ u(0,t)=b_i\\u(1,t)=c_i\\u(x,0)=d_i$$ $$i=1,2,3,4$$ if the following...
  12. R

    What is the largest number of mutually obtuse vectors in Rn?

    This is my question: What is the largest m such that there exist v1, ... ,vm ∈ ℝn such that for all i and j, if 1 ≤ i < j ≤ m, then ≤ vi⋅vj = 0 I found a couple of solutions online. http://mathoverflow.net/questions/31436/largest-number-of-vectors-with-pairwise-negative-dot-product...
  13. G

    Zettili QM Problem on Trace of an Operator

    Homework Statement In Zettili's QM textbook, we are asked to find the trace of an operator |\psi><\chi| . Where the kets |\psi> and |\chi> are equal to some (irrelevant, for the purposes of this question) linear combinations of two orthonormal basis kets. Homework Equations...
  14. TheMathNoob

    Graph theory (incidence matrix and linear algebra)

    Homework Statement I can't understand this paper. I understand the whole incidence matrix stuff, but I don't quiet get how it relates to the linear algebra. I don't know if this is allowed to do, but I will ask you questions line by line, so basically you will read the paper with me explaining...
  15. G

    Linear algebra: Find the span of a set

    Homework Statement Find the span of U=\{2,\cos x,\sin x:x\in\mathbb{R}\} (U is the subset of a space of real functions) and V=\{(a,b,b,...,b),(b,a,b,...,b),...,(b,b,b,...,a): a,b\in \mathbb{R},V\subset \mathbb{R^n},n\in\mathbb{N}\} Homework Equations - Span -Subset The Attempt at a Solution...
  16. G

    What is the defect of a linear transformation

    Homework Statement Question: What is the defect of a linear transformation? 2. The attempt at a solution A defective matrix (of a linear transformation) is a matrix that doesn't have a complete basis of eigenvectors. Does this mean that linearly dependent vectors of a matrix are called defects?
  17. G

    Linear algebra: Finding a basis for a space of polynomials

    Homework Statement Let and are two basis of subspaces and http://www.sosmath.com/CBB/latexrender/pictures/69691c7bdcc3ce6d5d8a1361f22d04ac.png. Find one basis of http://www.sosmath.com/CBB/latexrender/pictures/38d4e8e4669e784ae19bf38762e06045.png and...
  18. J

    Linear Algebra Which one of these Linear Algebra textbooks is the best?

    I want a good linear algebra textbook in order to learn to use linear algebra in physics but also to use it in more theoretical mathematics courses. I hope that with this poll i will also help others that want to study from a proper Linear Algebra textbook.
  19. B

    Linear Algebra Seeking a Advanced Linear Algebra Book (Required Topics)

    Dear Physics Forum personnel, I am currently reading the books called "Linear Algebra Done Right" by S. Axler and "Linear Algebra Done Wrong" by S. Treil. On the next semester, I will be taking the "Second Course in Linear Algebra" which will treat the following topics: determinants...
  20. G

    Linear algebra: Find the span of a set

    Homework Statement Find the span of U=\{2,\cos x,\sin x:x\in\mathbb{R}\} (U is the subset of a space of real functions) and V=\{(a,b,b,...,b),(b,a,b,...,b),...,(b,b,b,...,a): a,b\in \mathbb{R},V\subset \mathbb{R^n},n\in\mathbb{N}\} Homework Equations -Vector space span -Linear independence...
  21. Math Amateur

    MHB Simple Notational Issue in Roman: "Advanced Linear Algebra"

    I am reading Steven Roman's book, Advanced Linear Algebra and am currently focussed on Chapter 1: Vector Spaces ... ... I need help/clarification with respect to a notational issue regarding Roman's definition of the direct product and external direct sum of a family of vector spaces ... ...
  22. kostoglotov

    Should I bother with this last chapter of my Linear Algebra text?

    Intro to Lin. Alg via MIT OCW 18.06 (part of Electrical Engineering), by Gilbert Strang. I've been doing it as independent study before starting my BSEE next year. I'm getting to the end. Chapter 9 is titled "Numerical Linear Algebra", and is concerned with the heavy, intricate computational...
  23. G

    Find a basis and dimension of a vector space

    Homework Statement Find basis and dimension of V,W,V\cap W,V+W where V=\{p\in\mathbb{R_4}(x):p^{'}(0) \wedge p(1)=p(0)=p(-1)\},W=\{p\in\mathbb{R_4}(x):p(1)=0\} Homework Equations -Vector spaces The Attempt at a Solution Could someone give a hint how to get general representation of a vector...
  24. kostoglotov

    Polar and Jordan Decomp. in Intro to Linear Algebra?

    My Intro to LA course has visited the ideas of polar decomposition and Jordan forms, but not gone into them in depth. I wouldn't say I understood them, but I'm aware of them, and could possibly solve some basic exercises involving them if all I had to do was apply formulas. My question is...
  25. T

    Linear algebra - vector spaces, bases

    Homework Statement 1) In a vector space V of all real polynomials of third degree or less find basis B such that for arbitrary polynomial p \in V the following applies: [p]_B = \begin{pmatrix} p'(0)\\p'(1)\\p(0)\\p(1)\end{pmatrix} where p' is the derivative of the polynomial p. Homework...
  26. G

    Linear algebra: Check the statement

    Homework Statement Check the statement is true or false: Let \mathcal{A} : \mathbb{R^3}\rightarrow \mathbb{R^4} be a linear operator. If the minimum rank of \mathcal{A} is 2, than the maximum defect is 1. Homework Equations -Linear transformations The Attempt at a Solution Assume that...
  27. G

    How Does the Linear Operator \(\phi\) Transform Matrices to Polynomials?

    Homework Statement Let \phi:M_{2,2}\mathbb{(R)}\rightarrow \mathcal{P_2} be a linear operator defined as: (\phi(A))(x)=tr(AB+BA)+tr(AB-BA)x+tr(A+A^T)x^2 where B= \begin{bmatrix} 3 & -2 \\ 2 & -2 \\ \end{bmatrix} Find rank,defect and one basis of an image and kernel of linear operator...
  28. D

    What is the meaning of the term "dual"?

    Apologies if this is a really trivial question, but I've never been quite sure as to the usage of the terminology dual space. I get that given a vector space ##V## we can construct a set of linear functionals that map ##V## into its underlying field and that these linear functionals themselves...
  29. P

    Classify the fixed points of this dynamical system

    Homework Statement $$\dot{x_1}=x_2-x_2^3,~~~~~~\dot{x_2}=-x_1-3x_2^2+x_1^2x_2+x_2$$ I need help in determining the type and stability of the fixed points in this system. Homework Equations The Jordan Normal Form[/B] Let A be a 2x2 matrix, then there exists a real and non singular matrix M...
  30. N

    Linear algebra and differential equations advising

    Hey guys, I'm talking to my advisor soon and I was wondering if it is typical to, after taking multi variable calc, to take differential equations and linear algebra simultaneously? I'm going to have to be taking both modern physics and organic chemistry II as well, for context. Thanks everyone
  31. A

    I Question in linear algebra, derivation of a certain relation

    Hello good people, please refer to this: (notice the mistake in 9.31: cos(psi) switches places with cos(phi)sin(psi) to the best of my understanding) Now, I am trying to derive 9.30 and for this, according to the book, we solve 9.32. The problem is I can not understand 9.32, the meaning of...
  32. Pouyan

    What Is the Impact of Mapping in Linear Transformations from P2 to P3?

    Homework Statement Let T: P2 --> P3 be the transformation that maps a polynomial p(t) into the polynomial (t+5)p(t). a) find the image of p(t)= 2-t+(t^2) b) Find the matrix for T relative to bases {1,t,t^2} and {1,t,t^2,t^3}. Homework Equations Given The Attempt at a Solution a) I know...
  33. G

    Linear Algebra Book recommendations: Linear algebra

    Homework Statement What books of completely solved problems (free in pdf) in linear algebra would you suggest? Please suggest books that have solved problems, and not theory. Homework EquationsThe Attempt at a Solution
  34. D

    Diagonal Scaling of a 2x2 Positive Definite Matrix

    Given a Positive Definite Matrix ## A \in {\mathbb{R}}^{2 \times 2} ## given by: $$ A = \begin{bmatrix} {A}_{11} & {A}_{12} \\ {A}_{12} & {A}_{22} \end{bmatrix} $$ And a Matrix ## B ## Given by: $$ B = \begin{bmatrix} \frac{1}{\sqrt{{A}_{11}}} & 0 \\ 0 & \frac{1}{\sqrt{{A}_{22}}}...
  35. Abtinnn

    Is Im(A) Equal to Im(AV) for an Invertible Matrix V?

    Homework Statement [/B] If A is an mxn matrix, show that for each invertible nxn matrix V, im(A) = im(AV) Homework Equations none The Attempt at a Solution I know that im(A) can also be written as the span of columns of A. I also know that AV = [Av1 Av2 ... Avn] so im(AV) is the span of...
  36. ytht100

    A seemingly simple linear algebra equation that eludes me

    It is from some famous publications. But I seem can get it from rigorous proof after many hours and different methods of trying and Googling. If we have g as the eigenvector of a symmetric matrix and G is the eigenvalue of the symmetric matrix. \left[ {\begin{array}{*{20}{c}} {X11 -...
  37. X

    Best way to solve a system of complex equations?

    In my circuit analysis class I consistently need to solve system of complex equations, and I can't use MATLAB or anything for it. Suppose I have the following system: (Va-Vs)/(-j15) + Va/33 + (Va-Vo)/(-j25)=0 (Vo-Va)/(-j25) + (Vo-Vs)/10 = 0 What is the best way to solve it by hand in a time...
  38. S

    Are Hermitian Matrices with Specific Properties Traceless and Even-Dimensional?

    Homework Statement Consider hermitian matrices M1, M2, M3, M4 that obey the property Mi Mj + Mj Mi = 2δij I where I is the identity matrix and i,j=1,2,3,4 a) Show that the eigenvalues of Mi=+/- 1 (Hint: Go to the eigenbasis of Mi and use the equation for i=j) b) By considering the relation Mi...
  39. Q

    Finding a unitary transformation between two quantum states.

    I have to find a unitary transformation that takes me from one quantum state to another (or if there is such a transformation), given the two quantum states in matrix form. The matrices are huge (smallest is 16x16) , so doing it on paper is not an option. Does anyone know how I can do this in...
  40. B

    Describe all vectors orthogonal to col(A) with a twist

    I am trying to solve the following problem: Let A be a real mxn matrix. Describe the set of all vectors in F^m orthogonal to Col(A). Here, F^m could be C^m. Now in the real case, I'd say that the column space of A is the row space of A^T, and it is well known that the row space of a matrix is...
  41. S

    How to show if a given array of numbers is a vector?

    Homework Statement I'm reading Zee's book Einstein Gravity, I'm in the section where he said that given an array of two numbers p=(ap1, bp2), it is not a vector unless a=b. He just stated it without really showing how it must be like that. I know that a vector should satisfy a transformation...
  42. Math Amateur

    MHB Understanding Direct Products of Vector Spaces: Cooperstein's Example 1.17

    In Bruce Cooperstein's book: Advanced Linear Algebra, he gives the following example on page 12 in his chapter on vector spaces (Chapter 1) ... ...I am finding it difficult to fully understand this example ... ... Can someone give an example using Cooperstein's construction ... using, for...
  43. M

    Linear Algebra Proofs for Engineering Majors: A Fair Assessment?

    I'm grading for a linear algebra class this semester. The class is comprised entirely of engineering majors of various flavors. The homework assigned by the professor is almost entirely "proofs" they are fairly specific proofs. Really the only thing that designates them as proofs is that the...
  44. W

    Affine independence in terms of linear independence

    This question mostly pertains to how looking at affine independence entirely in terms of linear independence between different families of vectors. I understand there are quite a few questions already online pertaining to the affine/linear independence relationship, but I'm not quite able to...
  45. V

    Linear Algebra A book on tensors like Linear Algebra by Friedberg et al.

    Hi, I am looking for a book that explains tensors and builds a working knowledge of tensors, like the book Linear Algebra by Friedberg Insel and Spence, which I thought explained things very well (if you haven't heard of it, its an intro. book on linear algebra). Thanks!
  46. dsatkas

    Algebra Math textbooks for physics grad student and other questions

    I hope this post won't become too tedious. I've completed my undergrad studies in physics and if things go well i will begin my master's degree in April. The thing is, since my path to graduation has been peculiar (to say the least) I'm kinda weak in maths skills atm and need to improve. I'm...
  47. Andrew Pierce

    Determining subspaces for all functions in a Vector space

    Homework Statement First, I'd like to say that this question is from an Introductory Linear Algebra course so my knowledge of vector space and subspace is limited. Now onto the question. Q: Which of the following are subspaces of F(-∞,∞)? (a) All functions f in F(-∞,∞) for which f(0) = 0...
  48. W

    What math to learn after differential eq. and linear algebra?

    Hi, I'm currently studying to become a chemical engineer. After learning differential equation and linear algebra, I've realized how useful they are in my engineering courses since they make setting up equations and solving them so much easier. So I was wondering if there are other math that...
  49. J

    Matrix A and Vectors b & c in R^3: Solving Ax=b & Ax=c

    Homework Statement Construct a 3x3 matrix A and vectors b and c in R^3 so that Ax=b has a solution but Ax=c Homework EquationsThe Attempt at a Solution So I don't know where to start. I am not sure if the problem is asking me to create a matrix with real numbers or variables. What I do know is...
  50. C

    Markov chain: finding a general solution

    1. The problem statement Given a stochastic matrix P with states s_1...s_5: P = \begin{pmatrix} 1 & p_2 & 0 & 0 & 0\\ 0 & 0 & p_3 & 0 & 0\\ 0 & q_2 & 0 & p_4 & 0\\ 0 & 0 & q_3 & 0 & 0 \\ 0 & 0 & 0 & q_4 & 1 \end{pmatrix} and the matrix A (which is obviously related to P, but I can't see...
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