## 2250 7:30am Lectures Week 4 S2013

Last Modified: February 12, 2013, 05:37 MST.    Today: July 17, 2018, 17:24 MDT.
```Topics
The textbook definitions and theoremsEdwards-Penney 3.1, 3.2, 3.3 (3.0 K, txt, 07 Feb 2013)Edwards-Penney 3.4, 3.5, 3.6 (4.0 K, txt, 04 Feb 2013)```

### Monday: Linear Algebraic Equations. No matrices.

```Linear Algebraic Equations sections 3.1, 3.2
Frame sequence defined.
Theater 35mm movies project at 30 frames per second.A 35mm filmstrip (7.0 K, jpg, 12 Dec 2012)
Streaming video provider NetFlix uses frames to make a filmstrip,
each frame an image thumbnail of a DVD cover.A NetFlix Wii filmstrip (19.5 K, jpg, 12 Dec 2012)
Solutions to linear algebra problems can use a similar filmstrip
scheme, with the NetFlix DVD cover replaced by an image of a
completed solution step, called a frame.A filmstrip of 3 solution steps, called a frame sequence (68.3 K, pdf, 12 Dec 2012)
A frame sequence records the steps needed to solve a system of
equations. The steps are determined by a basic set of operations on
equations (the Toolkit).
Toolkit: combination, swap, multiply
Briefly: combo, swap, mult
Plane and space geometry: the meaning of simultaneous equations
The three possibilities
Unique solution
No solution
Infinitely many solutions
Method of elimination
Example: unique solution
x + 2y =  1
x -  y = -2
Example: no solution
x + 2y = 1
x + 2y = 2
Example: infinitely many solutions
x + 2y = 1
0 = 0
References:Slides: Intro Linear Equations, Toolkit, 3 Possibilities, Matrices (237.3 K, pdf, 15 Dec 2012)Slides: Unique solution case (110.1 K, pdf, 14 Dec 2012)Slides: No solution case (79.7 K, pdf, 03 Mar 2012)Slides: Infinitely many solutions case (131.1 K, pdf, 03 Mar 2012)Manuscript: Linear algebraic equations, no matrices (460.2 K, pdf, 10 Feb 2012)
Parameters in the general solution
Calculus: Parametric equation of a line or a plane.
Differential equations example, problem 3.1-26
y'' -121y = 0, y(0)=44, y'(0)=22
General solution given: y=A exp(11 x) + B exp(-11 x)
Substitute y into y(0)=44, y'(0)=22 to obtain a 2x2
system for unknowns A,B that has the unique solution
A=23, B=21.
Prepare 3.1 problems for next collection.
See problem notes section 3.1:html: Problem notes S2013 (5.1 K, html, 06 Dec 2012)
References for ER-1, ER-2 due next WeekExam Review: Problems ER-1, ER-2 (109.6 K, pdf, 04 Dec 2012)Transparency: Sample solution ER-1. (184.6 K, jpg, 08 Feb 2008)
More ReferencesTransparencies:  Ch3 Page 149+, Exercises 3.1 to 3.6 (869.6 K, pdf, 25 Sep 2003)Transparency: 3x3 Frame sequence and general solution (315.9 K, jpg, 12 Dec 2012)```

### Tuesday: Maple lab 2. Three Possibilities. No matrices.

``` Maple lab 2 problem 1
Discussion: Option 1: Freezing pipes maple lab 2
Problem: u' + ku = kA(t)
Integration methods
Tables
Maple
Links for maple lab 2:Option 1: Maple Lab 2, Newton cooling freezing pipes (240.5 K, pdf, 04 Dec 2012)Option 1: maple worksheet text freezing pipes (1.3 K, txt, 15 Mar 2012)Option 2: Maple Lab 2, Newton cooling swamp cooler (240.5 K, pdf, 04 Dec 2012)Option 2: maple worksheet text swamp cooler (1.3 K, txt, 15 Mar 2012)For more on superposition y=y_p + y_h, see Theorem 2 in the linkLinear DE part I (152.7 K, pdf, 07 Aug 2009)For more about home heating models, read the following links.Manuscript: Linear equation applications, brine tanks, home heating (374.2 K, pdf, 28 Jul 2009)Slides: Brink tanks (95.3 K, pdf, 04 Mar 2012)Slides: Home heating (109.8 K, pdf, 04 Mar 2012)
Lecture: 3.1, 3.2, 3.3
Topics
Frame sequence
Toolkit: combo, swap, multiply [EP 3.2]
Plane and space geometry
The three possibilities [EP 3.1]
Unique solution
No solution
Infinitely many solutions
Definitions
Free variable
Signal equation
Echelon form [EP 3.2]
The last frame test [EP 3.3]
The last frame algorithm [EP 3.2]
A detailed account of the three possibilities
Unique solution == zero free variables
No solution == signal equation
Infinitely many solutions == one+ free variables
How to solve a linear system
Toolkit: swap, combo, mult
Toolkit operations neither create nor destroy solutions!
Frame sequence examples
Computer algebra systems and error-free frame sequences.
How to use maple to make a frame sequence without errors.Help: Utah Maple Tutorial (2.0 K, html, 03 Dec 2012)
Solved Problems
Example 4 in 3.2
A:=Matrix([
[1,-2,3,2, 1],
[0, 0,1,0, 2],
[0, 0,0,1,-4]]);
b:=<10,-3,7>;
x1 - 2x2 + 3x3 + 2x4 +  x5 = 10,
x3       + 2x5 = -3,
x4 - 4x5 =  7
==> A is upper triangular; system is upper triangular
==> Solve by 3.2 Algorithm Back Substitution.
Back-substitution.
Warning:
The naming convention in the textbook [EP 3.2] differs from a
substantial number of references.Remarks on back-substitution 2013 (1.4 K, txt, 14 Dec 2012)
Back-Substitution, be it the textbook algorithm or another, should
be presented as combo operations in frames. Please avoid isolated,
incomplete algebraic gibberish.A gibberish example (1.2 K, txt, 13 Dec 2012)
DEFINITION
The leading variable in a equation is the first variable,
in variable list order, with a nonzero coefficient.
DEFINITION
A frame is echelon provided
(1) Each nonzero equation has a leading variable different from
all other equations.
(2) All variables preceding a leading variable, in variable list
order, are absent from all following equations.
DEFINITION
In an Echelon System the pivots are the coefficients of
the leading variables, in turn called pivot variables.
MATLAB EXPERTS Back-Substitution Example
Assume U is an nxm echelon (upper triangular) matrix with nonzero
diagonal entries U(i,i). Can you decode the following back
substitution algorithm for Ux=b, written in Matlab syntax?
n = length(b);
x = zeros(n,1);
for i=n:-1:1
x(i) = (b(i)-U(i,:)*x)/U(i,i);
end
NON-EXPERTS. The answer is expressed in terms of dot-products,
a COMBO operation.
Problem 3.2-24
The book's answer is wrong, it should involve k-4.
See references on 3 possibilities with symbol k.Beamer slides: 3 possibilities with symbol k (60.0 K, pdf, 31 Jan 2010)Slides: 3 possibilities with symbol k (98.8 K, pdf, 03 Mar 2012)Manuscript: Examples 11, 12 in Linear algebraic equations no matrices (460.2 K, pdf, 10 Feb 2012)Answer checks should use the online FAQ.html: Problem notes S2013 (5.1 K, html, 06 Dec 2012)?>

the solution, as in lecture examples. Expected is a sequence of
augmented matrices. Maple may be used to make the frames. A maple last
frame answer check is linalg[rref](A). Browse the Linear Algebra help
in the on-line tutorial:Help: Utah Maple Tutorial (2.0 K, html, 03 Dec 2012)
References for this lecture.Slides: Intro Linear Equations, Toolkit, 3 Possibilities, Matrices (237.3 K, pdf, 15 Dec 2012)Slides: Unique solution case (110.1 K, pdf, 14 Dec 2012)Slides: No solution case (79.7 K, pdf, 03 Mar 2012)Slides: Infinitely many solutions case (131.1 K, pdf, 03 Mar 2012)Manuscript: Linear algebraic equations, no matrices (460.2 K, pdf, 10 Feb 2012)```

## Wednesday: Augmented Matrix for System Ax=b. RREF. Last Frame Algorithm. Sections 3.3, 3.4.

```Topics
The textbook definitions and theoremsEdwards-Penney 3.1, 3.2, 3.3 (3.0 K, txt, 07 Feb 2013)Edwards-Penney 3.4, 3.5, 3.6 (4.0 K, txt, 04 Feb 2013)
Project: Switch from equations to matrices, which is the interface
for a computer algebra system [maple, mathematica] or a numerical
workbench [matlab, scilab].

Translation of equation models [EP 3.4]
Equality of vectors
Scalar equations to augmented matrix
Augmented matrix to scalar equations
Matrix toolkit: Combo, swap and multiply
Frame sequences for matrix models.
Last frame test for a matrix. The RREF of a matrix.
Last frame algorithm for a matrix.
Scalar form of the solution.
Vector form of the solution.
THEOREMS in 3.3
Theorem 1. RREF is unique
Theorem 2. Three possibilities
Theorem 3. More variables than equations ==> infinitely many
Theorem 4. Ax=0 has unique solution x=0 <==> rref(A)=I
Vector add and scalar multiply: componentwise
Matrix multiplication on paper.
Digital photographs.
Maxwell's RGB separation.
Photoshop operations and matrix algebra.
How to use maple to make frame sequences. No solution example 3.1-16.PDF: Maple frame sequence, no solution example (42.2 K, pdf, 08 Feb 2012)Maple Text: Maple code, frame sequence with no solution (0.5 K, mpl, 08 Feb 2012)Maple Text: Frame Sequence in maple, Exercise 3.2-14 (3.0 K, txt, 10 Feb 2012)
Answer checks should use the online FAQ.html: Problem notes S2013 (5.1 K, html, 06 Dec 2012)
References:Manuscript: Linear algebraic equations, no matrices (460.2 K, pdf, 10 Feb 2012)Slides: Intro Linear Equations, Toolkit, 3 Possibilities, Matrices (237.3 K, pdf, 15 Dec 2012)Manuscript: Matrix Equations (292.1 K, pdf, 07 Feb 2012)Slides: Matrix add, scalar multiply and matrix multiply (156.7 K, pdf, 03 Mar 2012)Slides: Digital photos, Maxwell's RGB separations, visualization of matrix add (170.2 K, pdf, 03 Mar 2012)Slides: More on digital photos, checkerboard analogy (141.9 K, pdf, 03 Mar 2012)```

### Thursday: Leif

``` Exam 1 review, questions and examples on exam problems 1,2,3,4,5.
Time permitting: Maple Lab 2, problems 1,2,3 details, due week 6.
Sample Exam: Exam 1 key from S2012. See also F2010, exam 1.Exams and exam keys for the last 5 years (19.6 K, html, 30 Apr 2013)```

### Friday: Frame Sequence to RREF. Last Frame Algorithm. Sections 3.2, 3.3, 3.4.

```Topics
The textbook definitions and theoremsEdwards-Penney 3.1, 3.2, 3.3 (3.0 K, txt, 07 Feb 2013)Edwards-Penney 3.4, 3.5, 3.6 (4.0 K, txt, 04 Feb 2013)
The three possibilities
The Toolkit: combo, swap, mult
Frame sequence
Last frame test for equations. Reduced echelon system.
coefficient one.
2. Zero equations are last
3. Lead variables are maintained in variable list order
Last frame test for matrices. Row reduced echelon form (RREF).
1. Each nonzero row has a leading one.
2. Zero rows are last
3. Leading ones are in columns of the identity matrix, called pivot
columns. These columns match the order of initial columns of the
identity matrix, but final columns may be missing.
Last frame algorithm
1. Apply the last frame test.
Proceed only if the system passes the test.
If in matrix form, then convert to a scalar system.
to the free variables.
4. Back-substitute the free variables into step 2.
5. Present the general solution as a list of variable
names in variable list order, with only invented
symbols on the right.
Example 1. The unique solution case
C:=Matrix([[1,2,1,1],[1,3,1,2],[1,1,2,3]]);
x + 2y + z = 1
x + 3y + z = 2
x + y + 2z = 3
Scalar form of the unique solution.
Why only lead variables in the last frame?
Why no free variables?
Example 2. The no solution case
C:=Matrix([[1,2,1,1],[1,3,1,2],[2,5,2,4]]);
x + 2y +  z = 1
x + 3y +  z = 2
2x + 5y + 2z = 4
We will find a signal equation
Example 3. The infinitely many solution case
C:=Matrix([[1,2,1,1],[1,3,1,2],[2,5,2,3]]);
x + 2y +  z = 1
x + 3y +  z = 2
2x + 5y + 2z = 3
Find the last frame
How many free variables? Count is called the RANK.
Apply the last frame algorithm
Example 4. The infinitely many solution case
C:=Matrix([[1,2,1,1],[3,6,3,3],[0,0,0,0]]);
x + 2y +  z = 1
3x + 6y + 3z = 3
0 = 0
Find the last frame
How many free variables?
Apply the last frame algorithm
Example 5. The infinitely many solution case
C:=Matrix([[0,0,0,0],[0,0,0,0],[0,0,0,0]]);
0 = 0
0 = 0
0 = 0
Find the last frame
How many free variables?
Apply the last frame algorithm

The three possibilities with symbol k.
x + ky = 2,
(2-k)x +  y = 3.
Examples with symbols.Slides: Three possibilities, theorems on infinitely many solutions, equations with symbols (129.0 K, pdf, 03 Mar 2012)Slides: 3 possibilities with symbol k (98.8 K, pdf, 03 Mar 2012)Beamer slides: 3 possibilities with symbol k (60.0 K, pdf, 31 Jan 2010)Manuscript: Examples 11, 12 in Linear algebraic equations no matrices (460.2 K, pdf, 10 Feb 2012)
Reading:Manuscript: Linear algebraic equations, no matrices (460.2 K, pdf, 10 Feb 2012)Slides: Intro Linear Equations, Toolkit, 3 Possibilities, Matrices (237.3 K, pdf, 15 Dec 2012)Slides: Unique solution case (110.1 K, pdf, 14 Dec 2012)Slides: No solution case (79.7 K, pdf, 03 Mar 2012)Slides: Infinitely many solutions case (131.1 K, pdf, 03 Mar 2012)Manuscript: Matrix Equations (292.1 K, pdf, 07 Feb 2012)Slides: Matrix add, scalar multiply and matrix multiply (156.7 K, pdf, 03 Mar 2012)Slides: Digital photos, Maxwell's RGB separations, visualization of matrix add (170.2 K, pdf, 03 Mar 2012)Slides: More on digital photos, checkerboard analogy (141.9 K, pdf, 03 Mar 2012)Slides: Inverse matrix, frame sequence method (97.9 K, pdf, 03 Mar 2012) ```

### More References Linear Algebra, Chapters 3, 4

`Chapters 3 and 4Slides: Last frame algorithm, Elimination, Rank, Nullity (156.3 K, pdf, 21 Dec 2012)Slides: Elementary matrix theorems (161.5 K, pdf, 03 Mar 2012)Slides: Three possibilities, theorems on infinitely many solutions, equations with symbols (129.0 K, pdf, 03 Mar 2012)html: Problem notes S2013 (5.1 K, html, 06 Dec 2012)Transparencies:  Ch3 Page 149+, Exercises 3.1 to 3.6 (869.6 K, pdf, 25 Sep 2003)Transparency: 3x3 Frame sequence and general solution (315.9 K, jpg, 12 Dec 2012)Maple: Lab 5, Linear algebra (170.0 K, pdf, 04 Dec 2012)Manuscript: Vectors and Matrices (426.4 K, pdf, 07 Feb 2012)Slides: vector models and vector spaces (144.1 K, pdf, 03 Mar 2012)Slides: Base atom, atom, basis for linear DE (117.6 K, pdf, 03 Mar 2012)Slides: Orthogonality (124.8 K, pdf, 03 Mar 2012)Slides: Partial fraction theory (160.7 K, pdf, 03 Mar 2012)Slides: The pivot theorem and applications (189.2 K, pdf, 03 Mar 2012)Text: Lawrence Page's pagerank algorithm (0.7 K, txt, 06 Oct 2008)Text: History of telecom companies (1.9 K, txt, 04 Apr 2013)html: Problem notes S2013 (5.1 K, html, 06 Dec 2012)`