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1 Why Set Theory
Set membership, union, intersection and complements form a language for a
precise description of mathematical ideas.1 Set theory is emphasized in mathematics since
the axiomatic method of analysis, more precisely the arithmetic properties of
integers, real numbers and functions can be logically codified and described in
it. Outside calculus, you may see the role of set concepts in some presentations
of analytic geometry. Lines, planes, surfaces and sometimes solid objects are
regarded as set of points. Sets and set membership also have a role in
combinatorics and counting, and in the combinatorial based parts of probability.
Combinatorics counts or is concerned with the number of ways objects in sets can
be grouped or placed together.
2 Set and Rule Viewpoints Reconciled
When two different views of an idea are presented, they need to be
reconciled. In the first instance, we could regard a function as a well-defined
computational rule on a domain. The rule could be given by a formula, and the
domain might be defined to the maximal set of real (or complex) numbers for
which division by zero and other undefined operations are avoided. A set of
ordered pairs which satisfies the vertical line property could be viewed as just
another (and then a more general way) of representing or defining a function.
Here
- a formula y = f(x) (or rule for computing y given
some x in a domain) can be used to define a set of order pairs with the
vertical line property, and
- a set with the vertical line property can be used to define a rule for
computing y when x lies in the domain of the set.
Graphing and sketching functions gives the opportunity to show the equivalence
between sets of ordered pairs with both the vertical and horizontal line
properties and one-to-one rules for computation. With this equivalence, graphs
and their transposes can define computation rules for functions or their
inverses.
The foregoing links together and treats equally the set-theoretic definition
of functions and the rule-based definition. The issue of which rule is better is
not important except in the set theoretic foundations of mathematics. Both
definitions should be viewed as interchangeable.
3 Relations
The use of the word relation in set theory requires some explanation. An
explanation is given here since, as suggested earlier, definitions and theories
without examples to illustrate them hold vacuously. Now requiring that an
equation be satisfied by (x,y) when giving the value of x
restricts the value of y, and vice-versa. The satisfaction of an equation
by two quantities (x,y) defines what is called a relationship
between them.
From equations to sets. For instance observe graphing and
sketching the solutions of an equation, for example y2+2x2
= 1, defines sets of ordered pairs (a solution set) in the plane. Requiring that
an equation be satisfied by the ordered pair (x,y) is equivalent
to requiring that this ordered pair belongs to the solution set of the equation.
In set theory, a set S of ordered pairs is said to be a relation: The
knowledge that a point (x,y) belongs to a set S links
(relates) the values of x and y. In particular, for a set S
of points in the plane, giving the value of x restricts the value of y
to the intersection of the set S with a vertical line through the point (x,0)
while specifying the value of y restricts the value of x to the
horizontal line through the point (0,y). This is exactly what happens
when S is a solution set for an equation.
Back to an Equation. Note given a set S of points,
we define the characteristic function XS of the set by
putting XS(x,y) = 1 whenever (x,y)
belong to the set S, and putting XS(x,y)
= 0 otherwise. Now the set S is the solution set of the artificial
equation XS(x,y) = 1. So we can go back
to the equation viewpoint of relations.
Footnotes:
1But it is not
always employed in mathematics instruction. In college-level calculus texts, the
set theoretic representation of functions may be mentioned or emphasized for
function of single variable, but it is frequently omitted in the description of
functions of several variables to science and engineering student for whom
specialization in math is no longer of interest.
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Three Skills
For
Algebra
Volume 2
Printed in Canada
ISBN 0-9697564-2-9
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Read slowly, this work may enrich your
skills & knowledge. Take the risk.
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Chapters and Appendices
Foreword 1. Introduction 2. Implication Rules [4] 3. Chains of Reason [3] 4. Induction Mathematical 4. Romeo and Juliet 6 Old Language 5 Knowledge Islands [2] 7 Arith Skill Check [4 X 2] Arith Webvideos 7. The Next Chapters 8 The Three Skills 8 VNR-Concise-Encyclopedia PS. What is a Variable [8] 9. Algebra Talk [7] 10 Two More Skills[5] 11 Why Shorthand 12 Shorthand Usage [10] 13 What's Next PS: The 4-th Skill For Algebra 14 Compound Interest [6] 15 Linear Equations [5] 16 Painless Proofs 17 Pythagoras PS I. Distributive Law PS II. Polynomials 18 Rules of Algebra [20] 19 Functions & Sets 20 Degrees & Radians 21 What's Next 22. Arith & Geometric Sums [2] 23 Summation Notation 24 Your Money [3] 25 Induction & Recursion [4] 26 What's Next 27 Pronouns in Logic 28 Occurrence Tables 29 Contrapositive 30 Truth Tables 31 Indirect Reason Pathways for Learning
Book Entrance
What is a Variable?
Introduction
Variation between Examples
Variation of Letters
A letter denotes a variable
Cases of Double Variation
Three Notions of a Variable
Constants, Parameters
& Variables
Talking about numbers
Dependent
or Independent
Variable, a Matter of Choice
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For
Senior
High School & Calculus Students
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Words to clearly
introduce algebra and variables
have been missing in course design. For people who cannot do
algebra,
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the missing words may
explain or ease their difficulties. Volume 2 ,Three
Skills for Algebra, in Chapters
8 to 14 & 18 etc, puts words before symbols to
providing the missing words in a way that enrich the
comprehension of all. Those words form the middle part of a algebra
(and logic) lessons aimed at helping or improving all
of high school mathematics and also calculus course
design & delivery.
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For Avid Readers in School & Out -
Online Books
1. Elements of
Reason. 1996
1A. Pattern
Based Reason 1995
1B. Math
Curriculum Notes 1996
2. Three
Skills for Algebra 1995
3.Why
Slopes & More.Math
1995
Tour their forewords.
Calculus Prep or Help: See Volumes 2 & 3,
and this bigger
Calculus
Guide. If your
calculus questions is not answered here, submit
it. Over time, that may complete the site development of
calculus.
For Parents: Speaking
Skills, Reading
& Writing,
Preparing for Science, ends,
values and methods for work and study, parent- friendly maths
skill development booklets for ages 4-14.
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Mostly
For High
School
Intro to Solving
Linear Equations
- a different paths for junior and even senior high
school students. Question for Tutors: When do
you use and when you skip the stick diagram method
here?
Fraction
Skills, thought-based development, Ages 10 to 14 may need a
tutor. Students who have to understand in order
to do may like the development in all or part.
For Senior
High School Mathematics & Calculus
5
wordy Logic
Chapters
4 curious Algebra
Chapters
Words before & besides symbols. A Key Algebra
forward & backwards Chapter
First Calculus
Preview (1st intro)
Four Calculus
Chapters
(2nd intro)
Intro to Complex
Numbers (long)
Intro to Mathematical
Induction (romantic & wordy at first)
Tutors & Instructors:
These lessons introduce skills differently Would you
recommend them?
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More Topics
1. Decimal
Arithmetic Reference!
2. Integers
- Intro to Signed No.s
3. Fractions
- fully explained.
4. Fractions
with Units
5. Number
Theory,
6. Solving
Linear Equations
7 Formulas
for- & backwards -
8. Proportionality,
Back- & For-wards.
9. Logic
Chapters:
10. Euclidean-Geometry
11. Slopes
& Equations of Straight Lines. (Take
I. See take II below)
12. Why
Study Slopes.
13. Maps,
Plans, Similarity & Trig,
(Take II included here)
14. Quadratics:
Starter lessons
15. Polynomials:
Starter lessons
16 Why
Factor Polynomials:
17 Functions
- Forwards & Backwards.
18. Exponents,
Radicals & logs.
19. Complex
Numbers before trig (new advance/ starter lesson)
20. DC
Electric
Circuits Etc
21. Real
Analysis
22. The
Olde Complex No, Trig
& Vector Section.
23. More
Calculus Stuff
- written after Volumes 2 and 3.
Level I Material: New Stuff
Time and Date Matters
Level I Arithmetic.
Money Matters
Measurement Matters
Matters of Chance (Risk Control)
Logic
Chapters
(leave what's not clear in Level I to Level II)
Using/Making Maps and Plans.
(A variant of
Maps,
Plans, Similarity & Trig, to
appear here).
For Instructors
-
Education
Essays
(opinions,
possibilities, references)
- Free
Advice and Directions for teaching primary & high school maths
will be given in online meeting place with voice &
whiteboard.
- Math & Logic How-TOs
1. Arithmetic
2. Algebra
3. More Algebra
4. Beginner Geometry
5. More Geometry
6. Calculus
7. Show Work or Logic
These may be too dense for students. Offering ideas to change
education makes this site different. Nothing
ventured, nothing gained. Site material is
mathematically correct, and where not, please report
errors. The two level program POMME in the site
entrance implies multiple paths for instruction. Supporting
those paths in turn implies a clear destination for
site development and perhaps a new name.
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