Calculus is the college or senior high school
mathematics subject required for college or university studies in accounting, business,
money matters, science, engineering and health.
Calculus employs at full strength most earlier
elements of high school mathematics:- functions, trig,
algebra (including polynomials),
mathematical induction, more logic, geometry and exact arithmetic met
briefly or fully in high school mathematics.
Calculus is very, very demanding. Half the
students who take college calculus fail.
Step (III) below is very long. So it and step IV
are switched.
Following these inserts, resume your normal methods for calculus
instruction as is
From 1983-89, before I left college
instruction for five years of work in applied mathematics, I tried to
make calculus easier for engineering and non-engineering students at the
junior college and university level. Calculus itself requires the
algebraic way of writing and reasoning met in high school at full
strength and beyond that introduces further demands, very, very suddenly
in a way that leads to algebraic shock. That being said,
easy max-min analysis of functions based on the relatively easy,
algebraic, sign analysis of derivatives appears in the middle of a
calculus course, and not at the start. By giving students formulas for
derivatives or slopes in factored form at the start of a calculus course
(even for students who have met calculus upto the level of the
chain-rule), we can develop algebraic reasoning skills more slowly
by providing a preview of differential calculus, geometric and
algebraic. That will ease a few fears and difficulties. Site
lessons on why slopes (Geometric
Preview) , Two logic puzzles (Implication
Rules) and Three Skills for
Algebra were all developed to ease or avoid fears and difficulties
of students entering calculus in fall 1983 in an effort to support
inductive principles for instruction.
Calculus students may start with weak arithmetic, weak
algebra and weak or imprecise reading and writing skills. Before any short
or complete review of high school mathematics, or further development of
calculus, try the following geometric and
algebraic calculus previews
The previews here provides a context for slope or derivative calculations,
while developing algebraic skills slowly. The algebraic preview here
in fact takes the easy elements of later chapters on application of derivatives
and put them first. That re-arrangement delays or slow the full-strength use of
algebraic ways of writing and reasoning in calculus, while preparing students
for it.
To tackle weak or imprecise reading and writing skills, digress from
calculus and present the two logic puzzle from this site's online chapter 2 on
Implication
Rules. Logic mastery (seeing the difference between one and two way
implication rules B if A (one way) and B if and only if A
(two-way) is a must for precision in reading and writing for calculus
and studies in general.
For a first assignment, give arithmetic review problems with
hints of algebra like the following to capturer and correct common arithmetic
errors and to further develop or reinforce student algebra skills.
Arithmetic & Algebra Review
Exercises to catch and correct common mistakes made by
students entering calculus.
Markers for my assignments would be told to catch and correct all errors
in notation and comprehension, so that my students have the chance to learn
from their mistakes.
That assignment could also include slope and further sign analysis problems
following the algebraic, calculus preview models.
(II). Insert to develop the algebraic viewpoint of limits
or their dependence on parameters variables
The section Limits via Algebra
in chapter 15 of the online volume Why
Slopes & More Math
include examples to help student make the transition from compute limits of the
Newtonian quotient
lim f(x+h) - f(x)
h-->0 h
for given values of x (say 2, 3, 5 and 7) to any value of x. That shows
how the slope or derivative of a function y = f(x) may regarded as a function of
x.
(IV) Employ as an Integral Calculus Preview
or starter lesson.
17 What
is Area
18
Integration
18
Area Calculation
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Chapter 17 and 18 offer a context for the
discussion of areas under curves plus statements of the
fundamental theorem of calculus. All this is done without
reference to summation notation for Riemann Sums
This summation notation free approach provides tutors
and teachers a simpler route for defining the definite integral as limit
of Riemann sums approximations to what area should be. |
(III). Insert to develop or avoid epsilons and delta view of limits, etc
The decimal perspective of limits, continuity and convergence
More sections from online volume Why
Slopes & More Math
The epsilon-delta viewpoint of limits, continuity and convergence requires
a high level of algebraic reasoning skills, too high for all students,
even those who will entering the study of pure mathematics. The
epsilon-delta viewpoint may be dropped without injury to students knowledge of
mathematics or preceded by a decimal viewpoint that requires the assumption of
decimal representation for real numbers. That assumption is needed
in present-day mathematics course designs or curricula which inherit the
decimal-free axiomitc viewpoint of real numbers present for the sake of purity,
if not practicality, in modern mathematics curricula of the mid-1950s and
onward. The latter curricula failed the general population in mathematics
by emphasizing an axiomatic structure for real numbers and the development of
algebra and calculus disjoint from common practices - use of decimals especially
- and without any sanction for those practices. As a student following the
modern mathematics curricula too literally, I sensed that separation and was disappointed
by a lack of sanction for mathematical practices which appear in daily life as
well as in the numerical examples met in calculus. The remedy I think is to
provide an applied mathematics curricula in which axioms for decimal
representation of real numbers and coordinates in 1, 2 and 3D are explicitly
assumed to sanction common practices. That sanction would go beyond the
reach of pure mathematics, but it would provide an axiomatic codification of
applied mathematics practices from arithmetic to the end calculus.
In that, axioms could be classified as pure or as applied, so that axiomatic
structure of modern mathematics is preserved. To learn more, see the text Calculus
by Lipman Bers (Holt, Rinehart and Winston 1969, SBN 03-065240-5).
Pure mathematics introduces a decimal-free or independent theory of
real numbers into studies for undergraduate mathematics degrees and into axioms
for real numbers met in high school and calculus. But first courses on calculus
today may use decimals to introduce and illustrate the concept of what is a
finite limit in examples while employing a decimal-free definition of limits and
continuity, and may call latter a more precise viewpoint. But in the practical
study of numerical methods and error control in calculations, decimal appear and
provide a more concrete, applied mathematics, approach to the definition and
discussion of limits, continuity and convergence. Chapter 14 in site
volume show or suggest how to make the definition, evaluation and
properties of limits, continuity and convergence easier to learn and teach with
greater simplicity and precision, modulo assumptions about the
representation of real numbers by decimal expansion and about the
convergence of the latter. The decimal viewpoint can stand alone, be
sufficient for most students. It can also be presented before the
epsilon-delta view to make the latter more accessible in enriched calculus
courses for gifted students, or in real analysis courses for undergraduate
students specializing in a quantitative discipline or mathematics.
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|
Volume 3, Why
Slopes & More Math |
Chapter 14 - Sections to Read.
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Chapter 14 - Excerpts.
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14 Limits & Error Control
and Continuityl
Details in Right Column
14 Limit of a Function
- [Play
Video] 4½ minutes: Algebraic View of Limits. Example
involving sums and quotients.
- [Play
Video] 5½ minutes: Limits and Error Control for Linear
Expressions
- [Play
Video] 2¾ minutes: Error Control to N decimal Places,
say 5 or 10.
- [Play
Video] 3¼ minutes: Limits as Error Control for an
unlimited number of decimal places.
14.
Jumps and Limited Error Control
Details in Right Column
14 Signif. Digit
Error Control
14 Cauchy Limits
- Decimal explanation of why
Cauch Sequence converge.
14 Limits
of Sequence- Decimal Viewpoint.
14 Decimal Arithmetic.
Sum, differences,
products and quotients of
real numbers represented by infinite decimal
expansions may be regarded as limits of the corresponding operations
on truncated decimal expansions. There-in a calculus level base to
complete the thought-based development of decimal arithmetic in a manner
sufficient and accessible to students not becoming mathematicians.
|
Limits, Error Control and Continuity
- [Play
Video] 4½ minutes: Algebraic View of Limits. Example
involving sums and quotients.
- [Play
Video] 2½ minutes: Algebraic Properties of
Limits I.
- [Play
Video] 2¼ minutes: Algebraic Properties of Limits II.
- [Play
Video] 5½ minutes: Limits and Error Control for Linear
Expressions
- [Play
Video] 2¾ minutes: Error Control to N decimal Places,
say 5 or 10.
- [Play
Video] 3¼ minutes: Limits as Error Control for an
unlimited number of decimal places.
Error control for the evaluation of functions y = f(x)
provides a simple context and motivation for continuity and convergence.
Continuity at Point
To explain the idea of continuity of a function y = f(x)
at a point x = a, we ask the following error-control
question with b = f(a): to what number m
of places should the decimal expansions of x and a agree,
for the decimal expansion of the number f(x) to agree with
that of b = f(a) to n-decimal places? That is,
given a whole number n, is there an m such that
| |x-a|
< d = |
1
2
|
· |
1
10m
|
implies
|f(x)-f(a)|
< e = |
1
2
|
· |
1
10n
|
(?) |
|
An affirmative answer requires that agreement of x
with a to m decimal places implies the agreement of f(x)
with f(a) to n decimal places. An affirmative answer
says unlimited accuracy and error control is possible at x = a.
The Greek letters d (delta) and e
(epsilon) above are employed here in accordance with tradition of some
(not all) calculus texts. For simplicity, the error control tolerances e
and d in the first instance here and below, may
be restricted to be numbers of the form [1/2] ·10-k
= [1/2] [1/(10k)]. The decimal free discussion of error
control and continuity dispenses with this requirement.
We say a function f(x) is continuous at a point x
= a if and only if unlimited error control is possible there. More
formally, we state the following definition.
Theorem 14.1 [Continuity at a Point] If f(x) is a
real-valued function of a real number x in an interval [c,d],
and a is a number in the interval [c,d] then the
function f is said to be continuous at the number x = a
if and only if the following holds. If for every n, there exist an m
such that
| |x-a|
< d = |
1
2 |
· |
1
10m |
implies |f(x)-f(a)|
< e = |
1
2 |
· |
1
10n |
· |
|
Decimal-Free Form
The decimal-free description or definition of continuity at a point x
= a is as follows.
[Continuity at Point] If f(x) is a real-valued function
of a real number x in an interval [c,d], and a
is a point in the interval [c,d] then the function f
is said to be continuous at x = a if and only if the
following holds: For every e1 >
0, there exist a d1 > 0 such that
| |x-a|
< d1
implies |f(x)-f(a)|
< e1 |
|
It is easily shown that the decimal-free and decimal-based definitions are
equivalent. The proof of equivalence, better left to a second reading of
this work, follows.
Proof of Equivalence.
To show the decimal-based description implies the decimal-free
description of continuity, observe the following. First given e1
> 0, there is an n > 0 such that e1
> [1/2]·[1/(10n)] = e.
The decimal-based requirement for continuity now is satisfied for some d
= [1/2] ·[1/(10m)]. So the decimal-free version holds
with d1 = d
= [1/2]·[1/(10m)].
Conversely, the other way that is, to show the latter decimal-free
form implies the decimal-based description of continuity, observe the
following. Given m > 0, let e1
= e = [1/2] ·[1/(10m)].
Then choose d1 > 0 so that the
decimal-free requirement is satisfied. The decimal-based version is then
satisfied if m > 0 is selected so that d1
³ d = [1/2] ·[1/(10m)].
Jumps and Limited Error Control
In some cases unlimited error control is not possible at the point x
= a. It fails in the following case:
There is an e > 0 such that for every d
> 0, there is some x satisfying the condition
|
|x-a|
< d and |f(x)-f(a)|
> e.
|
This means as the input x to the function y = f(x)
becomes a better approximation to the number a, there is no
guarantee the difference |f(x)-f(a)|
will be smaller than the error control target e.
This concept is illustrated by functions whose graphs have a few jumps in
them. The height of the largest jump near a point x = a
indicates how small the target tolerance e or
[1/2]·10-n can be in the
discussion of error control.
Again, unlimited error control is possible in the following
circumstances:
For each target tolerance e > 0, there is
a tolerance d > 0 such that the condition
|
|x-a|
< d and |f(x)-f(a)|
£ e.
|
These circumstances appear when f(x) is continuous at x
= a.
Computations on machines with finite accuracy precision arithmetic,
restrict the number n of decimals places that can be accurately
computed. Every computing machine which calculates to finitely many binary
or decimal places, suffers from such a limit. Small discontinuities in
calculations appear, except in those case where exact arithmetic can be
done. For example, on a computing machine which computes to at most n0
decimal places, the existence of a rule of the form
| |x-a|
< |
1
2 |
|
1
10m |
implies
|f(x)-f(a)|
< |
1
2 |
|
1
10n |
|
|
governing error cannot be guaranteed for n ³
n0 and can be considered improbable for most functions
evaluated numerical by a computer. An exception is provided by functions
whose numerically values can be represented (or encoded) exactly on a
machine.
On a computing machine which computes to at most n0
decimal places, the error control of a single addition and multiplication
are guaranteed to only n0 binary (or decimal) places.
Digits beyond the n0 place are uncertain. If several
such calculations are done, with numbers in one calculation being used in
the next, errors accumulate and accuracy is lost. The calculations in
question may have to be reorganized to improve accuracy.
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Calculus students & teachers need to know about methods
to ease algebra shock in calculus by starting with calculus previews, by
reviewing 3 skill for algebra, and by basing calculus concepts on the decimal
concepts alone or before decimal-free ones. First weeks of calculus often rush
through key elements of high school algebra - functions
especially.
To learn more, see site pages on calculus and, if you insist, on real analysis
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YOU are
better than YOU think. Show yourself how:
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// _ _ \\
/\
/\
<| (o) (o) |>
\ | |
/
|
Take
greater charge of your work or studies: Read like
a lawyer
for better work & study skills, but do not take
everything literally. |
| In
particular, two
logic puzzles
provide keys to site content, and to greater work and study
skills. Take a few moments to see if you agree. |
-/[]\-
||
/ \_
|||||||||||||||||||||||||||| |
Three Links for Teachers:
(i) First
Year High School Math - Lesson Plans with Fraction Focus
(ii) Second
Year High School Math - Lesson Plans with an algebra focus
(iii) Algebra
Lesson Plans
What may be learnt and when depends on how skills and
concepts are developed. Making the hard easier and clearer will allow earlier
& richer development of skills and concepts.
Help Me Learn/Teach;
- Algebra
words before symbols
- direct &
indirect use of formula, numerical versus algebraic solutions - what
is a variable (more words)
- Arithmetic
-new Arithmetic
Folder
- exercises
- with fractions
-
videos on primes, lcm, gcm,lcd, square roots etc
- Calculus - geometric
preview, algebraic
preview,
3 study guides,
much more
- Complex numbers
-starter lesson with java applet - easy
consequences for trig & vectors in the plane
- Education
- Empirical Course
Design & Delivery
- Fractions
- alone
- by rote
- with
algebra
- videos
- Functions - introduction
hindsight
- composition aka
substitution -
- Geometry, Euclidean - Correspondence
of triangles, Triangle
construction, duplication & Isometry - Failure
of ASA & the // line postulate - angle
sum in triangles -//
grams - Triangle
Similarity
- Geometry-
Analytic - functions, polynomials, complex numbers, unit circle
trigonometry
- Logic
- First Steps -
Symbols in
Logic -
Occurrence
& Truth Tables - Indirect
Reason -Indirect
Reason More
- Proportionality
- Definition
- Direct & Indirect Use - Numerical versus Algebraic Solutions
- Real Analysis
- Decimal View of concepts
and of proofs
- Rules &Patterns in Science, Technology & Society
- Pattern Based Reason
- Mathematical Reasoning, empirical, inductive or deductive
- Units
- in rates & slopes
& (?) derivatives
- in ratios
& proportions - slopes & rates included
- Complex Numbers & Vectors & Trig
- trig expression for
dot & cross - cosine
law
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