What is Linear algebra: Definition and 999 Discussions

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. smodak

    I Stupid Question about a Notation in Linear algebra

    I know the arrow -> means a map. For example, defines a linear map. But I cannot figure out what does a X mean? I know that above denote a inner product map. whatever is on the left of the : is defined by whatever is on the right. but what is the x symbol? What is the correct way to read...
  2. P

    Linear Algebra -- Projection matrix question

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  3. J

    Proving a set of matrices is NOT a vector space

    Homework Statement Show that the following is NOT a vector space: {(a, 1) | a, b, c, ∈ ℝ} {(b, c) Note: this is is meant to be a 2x2 matrix. This may not have been clear in how I formatted it. 2. The attempt at a solution I am self-studying linear algebra, and have had a difficulty...
  4. G

    I How this defines a linear transformation

    Admit that V is a linear space about \mathbb{R} and that U and W are subspaces of V. Suppose that S: U \rightarrow Y and T: W \rightarrow Y are two linear transformations that satisfy the property: (\forall x \in U \cap W) S(x)=T(x) Define a linear transformation F: U+W \rightarrow Y that...
  5. M

    Linear Algebra- Dependent or independent

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  6. Y

    Linear Algebra - Find Orthogonal Matrix Q that diagonals

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  7. A

    Linear algebra or intro to programming courses have higher failure rate?

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  8. tommyxu3

    I Can Normal Matrices Be Non-Self-Adjoint?

    Hello everyone, I have a question. I'm not sure if it is trivial. Does anyone have ideas of finding a matrix ##A\in M_n(\mathbb{C})##, where ##A## is normal but not self-adjoint, that is, ##A^*A=AA^*## but ##A\neq A^*?##
  9. a255c

    Lagrange optimization: cylinder and plane intersects,

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  10. joe_cool2

    Linear Algebra - Gram-Schmidt Process

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  11. Y

    Engineering Linear Algebra - Analysis of purely resistive DC circuit

    Homework Statement I'm trying to solve this circuit when I try to simulate and run a dc sweep i get that it can't be solved. When I try to find the answer using linear algebra I get this answer after I throw it into MATLAB with the warning “[w]arning: Matrix is close to singular or...
  12. L

    Similarity Transformation Involving Operators

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  13. Y

    Linear Algebra - Elimination Matrix when Permutation Needed

    Homework Statement I feel like I should know the answer to this, so I believe this to be an easy question. Say have matrix A, and I store the elimination matrices E_1,1 E_2,1 etc. and somewhere in the elimination process I have to use a permutation matrix to swap rows. My question is when I...
  14. Arnab Patra

    Find general equation of x′′(t)+5x′(t)+4x(t)=0

    Suppose ##x_1(t)## and ##x_2(t)## are two linearly independent solutions of the equations: ##x'_1(t) = 3x_1(t) + 2x_2(t)## and ##x'_2(t) = x_1(t) + 2x_2(t)## where ##x'_1(t)\text{ and }x'_2(t)## denote the first derivative of functions ##x_1(t)## and ##x_2(t)## respectively with respect to...
  15. Y

    Linear Algebra - Gram Schmidt & Normalization - Error in Sol

    Homework Statement So I think I found an error in the solution were it attempts to find q_2^ I'm asked find the orthornomal basis for the column space of matrix A. Homework EquationsThe Attempt at a Solution [/B] My question is in what it puts for q_2^ A_2 = [4/3 4/3 -2/3]^T ||A_2|| =...
  16. B

    I Eigen Vectors, Geometric Multiplicities and more....

    My professor states that "A matrix is diagonalizable if and only if the sum of the geometric multiplicities of the eigen values equals the size of the matrix". I have to prove this and proofs are my biggest weakness; but, I understand that geometric multiplicites means the dimensions of the...
  17. Y

    Linear Algebra - Projection of Vector

    Homework Statement I feel like this is a easy question but it seems the answer key doesn't seem to be right. So say I have 2 vectors and I'm trying to find the projection of vector u perpendicular to the vector v Homework EquationsThe Attempt at a Solution So I don't remember doing...
  18. Schwarzschild90

    Evaluating U(l) with Applied Linear Algebra: A Gambler's Demise

    Homework Statement I ask for help in solving the exercises in this project on applied linear algebra. The problem outlined in the project is one in which we are tasked with modeling the demise of a gambler. I need help solving exercise 1 (in red) on page 6. I have pasted the exercise text...
  19. Y

    Linear Algebra - Solving AC RLC circuit

    Homework Statement So yeah I'm doing a project were I get to create a problem. I would like to learn how to solve a AC RLC circuit using linear algebra. I'm trying to find all of the currents on the edges of the graphs and find all of the voltages at the nodes connecting the edges. I don't...
  20. micromass

    Schools In High School and Want to Do Advanced Mathematics? - Comments

    micromass submitted a new PF Insights post In High School and Want to Do Advanced Mathematics? https://www.physicsforums.com/insights/wp-content/uploads/2016/03/high school-math.png Continue reading the Original PF Insights Post.
  21. CynicusRex

    Studying Guidelines to studying linear algebra and statistics.

    I'll try to be concise. I've been out of math for years and never truly learned to understand it. Until now. I want to put the growth mindset theory to the test and see if I can handle physics (or any STEM field) on a university difficulty. To verify if I'm up to it and even have the slightest...
  22. F

    So what am I supposed to learn in linear algebra

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  23. Ismail Siddiqui

    [Linear Algebra] Conjugate Transpose of a Matrix and vectors in ℂ

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  24. P

    I Angles between complex vectors

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  25. B

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  26. polyChron

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    Hey, (I have already asked the question at http://physics.stackexchange.com/questions/244586/bloch-sphere-interpretation-of-rotations, I am not sure this forum's etiquette allows that!) I am trying to understand the following statement. "Suppose a single qubit has a state represented by the...
  27. C

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  28. Z

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  29. V

    I Confusion about Dual Basis Vectors: Why are these two relationships equal?

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  30. BobTheLawyer

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  31. T

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  32. G

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    Homework Statement Solve the linear system of equations: ax+by+z=1 x+aby+z=b x+by+az=1 for a,b\in\mathbb R and plot equations and solutions in cases where the system is consistent. Homework Equations -Cramer's rule -Kronecker-Capelli's theorem The Attempt at a Solution Using Cramer's rule, we...
  33. G

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  34. M

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  35. Y

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  36. Y

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  37. Prof. 27

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  38. K

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  39. R

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  40. G

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  41. R

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  42. G

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  43. G

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  44. J

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  45. Duncan R

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  46. Q

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  47. F

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  48. P

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  49. C

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  50. G

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