2240 class highlights

  • Wed Jun 28 Send me a private forum posting on ASULearn to tell me what topic you have chosen. Use class time to work on the project components. I'll be on Zoom at 8pm if there are any questions.
  • Tues Jun 27 Test 2. Spend the remaining time on the final project.
  • Mon Jun 26
    final project presentations. MathSciNet Hill cipher. Leontief. Search within matrix/matrices. Google Scholar. eigenvalue in mathematics education research.
    success, Review, Test 2 review, topics to study, Test 1 review
    Practice test, problem sets, hw problems, clickers, study guide topics, glossaries. Solutions exist for you to compare and learn from but be sure to try them on your own and make sure you can discuss the concepts and do the problems (linearly +) independently!
  • Fri Jun 23
    Clicker questions---review of eigenvectors
    engagement
    course goals
    uncover the mystery of inverse(P).A.P=?, Diagonalization and apply to computer graphics
    Applications to mathematical physics, quantum chemistry..., Eigenfunction, Tacoma Narrows
    final research presentations
    MathSciNet Hill cipher. Leontief. Search within matrix/matrices Chinese, German Gauss, French Laplace, German polymath Hermann Grassman (1809-1877) 1844: The Theory of Linear Extension, a New Branch of Mathematics (extensive magnitudes---effectively linear space via linear combinations, independence, span, dimension, projections.)
    paper evaluations

  • Thur Jun 22
    Clicker questions--- eigenvector decomposition (5.6) part 2
    Dynamical Systems and Eigenvectors
    comic
    THE $25,000,000,000 EIGENVECTOR by Kurt Bryan and Tanya Leise
    About once a month, Google finds an eigenvector of a matrix that represents the connectivity of the web (of size billions-by-billions) for its pagerank algorithm.
    http://languagelog.ldc.upenn.edu/nll/?p=3030
    presentation session, final research presentations Chinese,
    Hamburger earmuffs and the pickle matrix
    sample project,
    full guidelines
    rubric for the final project

  • Wed Jun 21
    Clicker questions in 5.1#1-3
    Review algebra of eigenvalues and eigenvectors and Eigenvector decomposition
    Review first example on Dynamical Systems and Eigenvectors
    Clicker questions on eigenvector decomposition (5.6) part 1#3-4
    Highlight predator prey, predator predator or cooperative systems (where cooperation leads to sustainability) [Solutions: 1. a), 2. c), 3. c), 4. b)]
    Geometry of Eigenvectors
    Ex1:=Matrix([[0,1],[1,0]]);
    Eigenvalues(Ex1);
    Eigenvectors(Ex1);

    Ex2:=Matrix([[0,1],[-1,0]]);
    Ex3:=Matrix([[-1,0],[0,-1]]);
    Ex4:=Matrix([[1/2,1/2],[1/2,1/2]]);
    Horizontal shear Matrix([[1,k],[0,1]])
    Dynamical Systems and Eigenvectors

  • Tues Jun 20 Take questions on 2.8
    algebra of eigenvalues and eigenvectors and connect to geometry eigensheep comic
    Eigenvalues of triangular matrices like shear matrix are on the diagonal-- characteristic equation.
    Matrix([[2,1],[1,2]])
    M := Matrix([[2,1],[1,2]]);
    Eigenvectors(M);

    Eigenvector comic 1
    Begin 5.6: Eigenvector decomposition for a diagonalizable matrix A_nxn [where the eigenvectors form a basis for all of Rn].
    M := Matrix([[6/10,4/10],[-125/1000,12/10]]);
    Eigenvectors(M);

    Application: Foxes and Rabbits
    Also revisit the black hole matrix.
    Clicker questions on eigenvector decomposition (5.6) part 1#1-2
    Compare with Dynamical Systems and Eigenvectors first example

  • Mon Jun 19 Take questions on determinants.
    Clicker questions in Chapter 3 9
    If space is the final frontier, then what's a subspace? subspace, basis, null space and column space
    nullspace
    clicker in 2.8 1-3
    algebra of eigenvalues and eigenvectors and connect to geometry
  • Fri Jun 16
    Review linear transformations of the plane, including homogeneous coordinates
    Review Laplace expansion and row operations and determinants via Clicker questions in Chapter 3 #10
    The relationship of row operations to the geometry of determinants - shear matrices preserve area, volume.
    Clicker questions in Chapter 3 4-8
    revisit determinant of product
    If space is the final frontier, then what's a subspace? basis, null space and column space
    Engagement and exam corrections

  • Thur Jun 15 Test 1

  • Wed Jun 14
    Clicker questions in Chapter 3 #1-3
    2x2 and 3x3 diagonals methods and Laplace's expansion (1772 - expanding on Vandermonde's method) method in general. [general history dates to the Chinese and Leibniz]
    M:=Matrix([[a,b,c],[d,e,f],[g,h,i]]);
    Determinant(M); MatrixInverse(M);
    M:=Matrix([[a,b,c,d],[e,f,g,h],[i,j,k,l],[m,n,o,p]]);
    Determinant(M); MatrixInverse(M);

    LaTex Beamer slides
    The determinator comic, which has lots of 0s
    The connection of row operations to determinants
    The determinant of A transpose and A triangular (such as in Gaussian form).
    The determinant of A inverse via the determinant of the product of A and A inverse - and via elementary row operations - so det A non-zero can be added into Theorem 8 in Chapter 2: What Makes a Matrix Invertible.
    Mention google searches: application of determinants in physics application of determinants in economics application of determinants in chemistry application of determinants in computer science Eight queens and determinants application of determinants in geology: volumetric strain
    review slides, study guide, sample partial test

  • Tues Jun 13
    Review linear transformations of the plane, including homogeneous coordinates
    Clicker questions in 2.7 #3-6
    Computer graphics demo [2.7] Examples 3-5
    rotation matrix and 6.1
    Application of 2.7 and 6.1: Keeping a car on a racetrack
    Begin Yoda (via the file yoda2.mw) with data from Kecskemeti B. Zoltan (Lucasfilm LTD) as on Tim's page
    Clicker questions in 2.7 #7, 8 and 9

  • Mon Jun 12
    Clicker 2.3 review
    Applications of 2.1-2.3: 1.8 (p. 62, 65, & 67-68), 1.9 (p. 70-75), and 2.7
    Linear transformations
    Guess the transformation. In the process, discuss that the first column of the matrix representation is the same as the output of the unit x vector, and that invertible matrices will take the plane to the plane (the range is onto the plane), while matrices that are not invertible do not span the entire plane, so they smush the plane (pictures in the plane, etc).
    Mirror mirror comic and Sheared Sheap comic
    Glossary of terms
    general geometric transformations on R2 [1.8, 1.9]
    In the process, review the unit circle
    Computer graphics demo [2.7] Examples 1-2
    Clicker questions in 2.7 #1-2
  • Fri Jun 9
    Clicker questions in 2.2 #1-3
    2.1 #23: Assume CA=I_nxn. A doesn't have to be square. 3x2 matrix A.
    2.2 #21: Explain why the columns of an nxn matrix A are linearly independent when A is invertible.
    problematic reasoning: If the 2 columns of A are multiples the determinant will be 0
    incomplete reasoning: the columns of A are li because Ax=0 has only the trivial solution when A is invertible (why?).
    Theorem 8 in 2.3 [without linear transformations]: What makes a matrix invertible
    Discuss what it means for a square matrix that violates one of the statements. Discuss what it means for a matrix that is not square (all bets are off) via counterexamples.
    -2.1-2.3 Applications: Hill Cipher, Condition Number and Linear Transformations (2.3, 1.8, 1.9 and 2.7)
    Introduction to Linear Maps
    Hill Cipher history
    Maple file on Hill Cipher and Condition Number and PDF version
    review of Hill cipher and condition number
    Clicker questions in 2.2 #4-5
    Clicker questions in 2.3 and Hill Cipher and Condition Number

  • Thur Jun 8
    clicker review questions 9-10
    Review 2.2 Algebra: Inverse of a matrix
    Clicker in 2.1 and 2.2: #7 onward
    Applications of multiplication and the inverse (if it exists)
    Show that if the columns of a square nxn matrix A span the entire R^n, then A is invertible.
    In groups of 2-3 people, assume that A (square) has an inverse. What else can you say?
    Theorem 8 in 2.3 [without linear transformations]: What makes a matrix invertible
    Discuss what it means for a square matrix that violates one of the statements. Discuss what it means for a matrix that is not square (all bets are off) via counterexamples.

  • Wed Jun 7
    matrix multiplication and matrix algebra
    Introduce transpose of a matrix via Wikipedia, including Arthur Cayley. Applications including least squares estimates, such as in linear regression, data given as rows (like Yoda).
    twobytwo := Matrix([[a, b], [c, d]]);
    MatrixInverse(twobytwo);
    MatrixInverse(twobytwo).twobytwo
    simplify(%)

    comic. Find the identity of superman
    2.2 Algebra: Inverse of a matrix.
    Repeated methodology: multiply by the inverse on both sides, reorder by associativity, cancel A by its inverse, then reduce by the identity to simplify.
    Comic: associativity superpowers
    Steps, The Science of Successful Learning, learn something new
    clicker review questions 3-8

  • Tues Jun 6
    Clicker question in 1.3 and 1.5 #5
    dependence comic
    Review 1.5 and 1.3 and 1.7 vector and matrix equations
    Roll Yaw Pitch Gimbal lock on Apollo 11.
    Maple commands Maple file file
    Review 1.1, 1.2, 1.3, 1.4, 1.5, 1.7
    Begin Chapter 2:
    Image 1   Image 2   Image 3   Image 4   Image 5   Image 6   Image 7.
    glossary for 2.1-2.3
    Then 2.1 question, matrix multiplication and matrix algebra. AB not BA...

  • Mon Jun 5
    Clicker questions in 1.3 and 1.5 # 4
    discuss what happens when we correctly use GaussianElimination(s13n15extension) - write out the equation of the plane that the vectors span.
    s13n15extension:=Matrix([[1,-5,b1],[3,-8,b2],[-1,2,b3]]);
    GaussianElimination(s13n15extension);

    M:=Matrix([[1,-5,0,b1],[3,-8,0,b2],[-1,2,1,b3]]);
    GaussianElimination(M);
    a:=spacecurve({[t, 3*t, -1*t, t = 0 .. 1]}, color = red, thickness = 2):
    b:=spacecurve({[-5*t, -8*t, 2*t, t = 0 .. 1]}, color = blue, thickness = 2):
    diagonalparallelogram:=spacecurve({[-4*t, -5*t, -1*t, t = 0 .. 1]}, color = black, thickness = 2):
    c:=spacecurve({[-4*t, -5*t, 3*t, t = 0 .. 1]}, color = magenta, thickness = 2):
    display(a,b,c,diagonalparallelogram);

    Modified the diagonal of the parallelogram by changing the last coordinate to get a vector out of the plane.
    Review 1.3 and 1.4, and theorem 4 in 1.4.
    1.5: vector parametrization equations of homogeneous and non-homogeneous equations. Introduce t*vector1 + vector2 is the collection of vectors that end on the line parallel to vector 1 and through the tip of vector 2. parallelvectorline movie.
    Clicker question to motivate 1.7
    How to express redundancy?
    1.3 and 1.7 vector and matrix equations
    In R^2: spans R^2 but not li, li but does not span R^2, li plus spans R^2.
    Clicker questions in 1.7 and the theorem about l.i. equivalences in 1.7.
  • Fri Jun 2 Review vectors, addition, scalar multiplication, linear combinations and span of them, and movie visualizations.
    What's your span? comic
    Clicker questions in 1.3 and 1.5 # 3
    Begin 1.4. Ax via using weights from x for columns of A versus Ax via dot products of rows of A with x and Ax=b the same (using definition 1 of linear combinations of the columns) as the augmented matrix [A |b]. The matrix vector equation and the augmented matrix. The matrix vector equation and the augmented matrix and the connection of mixing to span and linear combinations.
    Theorem 4 in 1.4
    Clicker question in 1.4
    Coff:=Matrix([[.3,.4,36],[.2,.3,26],[.2,.2,20],[.3,.1,18]]);
    ReducedRowEchelonForm(Coff);
    Coffraction:=Matrix([[3/10,4/10,36],[2/10,3/10,26],[2/10,2/10,20],[3/10,1/10,18]]);
    ReducedRowEchelonForm(Coffraction);

    Decimals (don't use in Maple) and fractions. Geometry of the columns as a plane in R^4, of the rows as 4 lines in R^2 intersecting in the point (40,60).

  • Thur Jun 1
    Review the algebra and geometry of eqs with 3 unknowns in R^3.
    Clicker questions 1.1 and 1.2 #6 onwards
    History of linear equations and the term "linear algebra" images, including the Babylonians 2x2 linear equations, the Chinese 3x3 column elimination method over 2000 years ago, Gauss' general method arising from geodesy and least squares methods for celestial computations, and Wilhelm Jordan's contributions.
    Gauss quotation. Gauss was also involved in other linear algebra, including the history of vectors, another important "linear" object.
    Glossary 2: More Terms for Test 1
    vectors, scalar mult and addition, Foxtrot vector addition comic by Bill Amend. November 14, 1999.
    1.3 linear combinations and weights, vector equations and connection to 1.1 and 1.2 systems of equations and augmented matrix. linear combination language (addition and scalar multiplication of vectors).
    c1*vector1 + c2*vector2_on_a_different_line is a plane via:
    span1:=Matrix([[1, 4, b1], [2, 5, b2], [3, 6, b3]]);
    GaussianElimination(span1);

    Comment on the span being b1-2b2+b3=0. Notice that Vector([7,8,9]) also satisfies this equation
    a1:=spacecurve({[t, 2*t, 3*t, t = 0 .. 1]}, color = red, thickness = 2):
    a2:=textplot3d([1, 2, 3, ` vector [1,2,3]`], color = black):
    b1:=spacecurve({[4*t,5*t,6*t,t = 0 .. 1]}, color = green, thickness = 2):
    b2:=textplot3d([4, 5, 6, ` vector [4,5,6]`], color = black):
    c1:=spacecurve({[7*t, 8*t, 9*t, t = 0 .. 1]},color=magenta,thickness = 2):
    c2:=textplot3d([7,8,9,`vector[7,8,9]`],color = black):
    display(a1,a2,b1,b2,c1,c2);

    Replace with [7, 8, 10] which is not in the span.
    Clicker questions in 1.3 and 1.5 # 1-2

  • Wed May 31 Turn in hw.
    Gaussian and Gauss-Jordan for 3 equations and 2 unknowns in R2.
    Engagement with the i-clickers (Think, Pair up, Share, Review and Add), where to get help, solutions and glossary on ASULearn.
    Clicker questions 1.1 and 1.2 #1
    Gaussian and Gauss-Jordan or reduced row echelon form in general: section 1.2, focusing on algebraic and geometric perspectives and solving using by-hand elimination of systems of equations with 3 unknowns. Follow up with Maple commands and visualization: ReducedRowEchelon and GaussianElimination as well as implicitplot3d in Maple (like on the handout):
    Parametrize x+y+z=1.
    with(plots): with(LinearAlgebra):
    implicitplot3d({x+y+z=1, x+y+z=2}, x = -4 .. 4, y = -4 .. 4, z = - 4 .. 4);
    Ex1:=Matrix([[1,-2,1,2],[1,1,-2,3],[-2,1,1,1]]);
    implicitplot3d({x-2*y+z=2, x+y-2*z=3, (-2)*x+y+z=1}, x = -4 .. 4, y = -4 .. 4, z = -4 .. 4);
    Ex2:=Matrix([[1,2,3,3],[2,-1,-4,1],[1,1,-1,0]]);
    implicitplot3d({x+2*y+3*z=3,2*x-y-4*z=1,x+y-z=0}, x=-4..4,y=-4..4,z=-4..4);
    Ex3:=Matrix([[1,2,3,0],[1,2,4,4],[2,4,7,4]]);
    implicitplot3d({x+2*y+3*z = 0, x+2*y+4*z = 4, 2*x+4*y+7*z = 4}, x = -13 .. -5, y = -1/4 .. 1/4, z = 3 .. 5, color = yellow);
    Ex4:=Matrix([[1,3,4,k],[2,8,9,0],[10,10,10,5],[5,5,5,5]]);
    GaussianElimination(Ex4);
    Ex4a:=Matrix([[1,3,4,k],[2,8,9,0],[10,10,10,5],[5,5,5,5]]);
    GaussianElimination(Ex4);

    Highlight equations with 3 unknowns with infinite solutions, one solution and no solutions in R3, and the corresponding geometry, as we review new terminology and glossary of terms
    Clicker questions 1.1 and 1.2 continued
    Advice from previous students
    2240 engagement

  • Tues May 30 UTAustinXLinearAlgebra.mov. Manga comic
    Course intro slides # 1 and 2
    Work on the introduction to linear algebra handout motivated from Evelyn Boyd Granville's favorite problem (#1-3). At the same time, begin 1.1 (and some of the words in 1.2) including geometric perspectives, by-hand algebraic EBG#3, Gaussian Elimination and EBG #5 and pivots, solutions, plotting and geometry, parametrization and GaussianElimination in Maple for systems with 2 unknowns in R2.
    Evelyn Boyd Granville #3:
    with(LinearAlgebra): with(plots):
    implicitplot({x+y=17, 4*x+2*y=48},x=-10..10, y = 0..40);
    EBG3:=Matrix([[1,1,17],[4,2,48]]);
    GaussianElimination(EBG3);
    ReducedRowEchelonForm(EBG3);

    In addition, do #4
    Evelyn Boyd Granville #4: using the slope of the lines, versus full pivots in Gaussian (r2'=-4 r1 + r2):
    EBG4:=Matrix([[1,1,a],[4,2,b]]);
    GaussianElimination(EBG4);


    Course intro slides continued.
    How to get to the main calendar page: google Dr. Sarah / click on webpage / then 2240. Discuss webpages, homework and Polya's How to Solve it
    Vocabulary/terms/ASULearn glossary

    Evelyn Boyd Granville #5 with k as an unknown but constant coefficient.
    EBG#3, Gaussian Elimination and EBG #5
    EBG5:=Matrix([[1,k,0],[k,1,0]]);
    GaussianElimination(EBG5);
    ReducedRowEchelonForm(EBG5);

    Prove using geometry of lines that the number of solutions of a system with 2 equations and 2 unknowns is 0, 1 or infinite.

    Review Gaussian and Gauss-Jordan for 3 equations and 2 unknowns in R2.

    Drawing the line comic. Solve the system x+y+z=1 and x+y+z=2 (0 solutions - 2 parallel planes)
    implicitplot3d({x+y+z=1, x+y+z=2}, x = -4 .. 4, y = -4 .. 4, z = - 4 .. 4)