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Chapter 4. Longer Chains of Reason
Previous Chapter: Chains of Reason
This chapter explains one version of inductive5
reason: the recursive or repetitive approach to putting one-way implication
rules together, one after another.
To induce means to extract. Induction here consists of extracting
conclusions from chains of rules and patterns, one after another, perhaps
without stopping or end. Another form or version of inductive reason is
concerned with the extraction of patterns from experience and observation. See
the last words of the previous chapter.
This chapter ends with a description of the principle of mathematical
induction - another method for obtaining conclusions used only in mathematical
arguments or computations. There is more to mathematics than just doing
arithmetic.
Recall that rules, which say that when a first situation occurs so
should a second, are called implication rules. Implication rules can be
linked together, one after another. A ladder-based story illustrates the
underlying idea. It is called induction. This story leads to the notion called
mathematical induction, a method of reason or logic used in mathematics after
arithmetic to get conclusions (or climb ladders). The method is described first
with words, a simple story, and then with some shorthand notation.
Romeo and Juliet
Imagine a hero, Romeo, riding a horse towards a tall building (a castle).
There is a ladder up the side of the building leading to the room where Juliet
lives. The bottom step of the ladder is two meters or more (several feet or
more) away from the ground. The ladder is not broken. It is in good condition. A
person getting to each step of the ladder can climb to the next. Question: Can
an able-bodied individual, Romeo, reach Juliet via the ladder? The answer is yes
provided Romeo can get to the first or bottom-most step of the ladder. It is
no otherwise. The main logic-related ideas in this brief story are as
follows.
- There is a long ladder to be climbed.
- When any one step is reached, the next step can be reached. (The ladder
must be in good condition for this to hold).
- The first or bottom-most step can be reached.
This situation implies we (or Romeo) can reach each step of the ladder.
Note that the long ladder may have a finite number of steps, for example 183.
Then we (or Romeo) can with enough time and patience, reach the last one, or any
step in between.
On the other hand, we can imagine a ladder could have an infinite number of
steps. For each step we take, a next is possible. For instance, the whole
numbers we use for counting do not stop. Each whole number is followed by
another - just add 1.
Now suppose or imagine we have a sequence of steps, a ladder, which goes on
and on without stopping. Then with enough time and patience, we can reach anyone
you mention. An example is met in counting. We can begin counting with the
number 1, then 2, then 3 and so on.
When we begin to count, we may have only a finite number of objects to count.
With a long enough life, and enough patience, the count will end. But if we
count minutes there will always be one more to count. This minute count will
never end. More precisely, each of us counters may end, but the counting of
minutes in principle can continue. That is, this minute count can reach any
large number you specify in advance with or without you. In principle all
minutes after the beginning of the count will be met and counted.
To rephrase the above, on a ladder (or road) with finitely or infinitely many
steps, the first step needs to be reachable. And from each step, the next step
needs to be reachable. When this occurs, any whole number of steps along the
road or ladder in question is reachable.
In practice, if each step takes time, the number of steps
reachable will depend on how much time is available. Reach-ability here does
not take into account the amount of time available, albeit people doing
numerical computations on electronic computers must consider the latter.
CAUTION. The conclusion that all steps can be climbed or reached does not
follow from the principle of mathematical induction if the ladder is broken, or
if the first step is not reachable or if a tornado comes along, or if you
break your ankle, etc. Check for these nasty situations when you want to use
this principle to get a conclusion.
Reading Guide
The principle of mathematical induction stated below describes the above ladder
idea in the algebraic shorthand notation favored in mathematics. The last part
of this chapter will not make sense to you if you are not familiar with this
shorthand notation. If this is the case, you may skip this description of
mathematical induction. If you read it, and you find that you do not understand
it, you could return to it later after you have seen the following chapters on
algebra. They explain the use of shorthand in algebra.
Next Section: 4. Induction
Mathematical
Next Chapter: 5. Islands and Division of Knowledge, How
knowledge divides
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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
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Guide. If your
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For Parents: Speaking
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Mostly
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Intro to Solving
Linear Equations
- a different paths for junior and even senior high
school students. Question for Tutors: When do
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here?
Fraction
Skills, thought-based development, Ages 10 to 14 may need a
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For Senior
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Words before & besides symbols. A Key Algebra
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First Calculus
Preview (1st intro)
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These lessons introduce skills differently Would you
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More Topics
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Chapters:
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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
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Level I Material: New Stuff
Time and Date Matters
Level I Arithmetic.
Money Matters
Measurement Matters
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Logic
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Using/Making Maps and Plans.
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appear here).
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Essays
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possibilities, references)
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These may be too dense for students. Offering ideas to change
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entrance implies multiple paths for instruction. Supporting
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