Appetizers and Lessons for Mathematics and Reason (www.whyslopes.com)
||Définition d'une variable || Algèbre || Arithmetique || Logique ||La raison basée sur les règles et modelés||

Online Volumes
1,  Elements of Reason.
1A. Pattern Based Reason 
1B. Math Curriculum Notes
2. Three Skills for Algebra
3. Why Slopes & More Math

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YOU are better than YOU think. Show yourself  how:  

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Read  logic chapters 1 to 5  in online volume Three Skills for Algebra  for greater skills & confidence in  work 
and study

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 Logic chapters 1 to 5  re- appear not in sequence, as is or longer,  in  Volume 1A,  Pattern Based Reason, Bon Appetite.

Logic Mastery
 Amazing, Amusing, Amorous,  Delicious, Delightful, Edifying, Strengthening Elixir. 
It eases work & learning difficulties Makes the hard easier. Opens eyes. Leads to greater precision.
in reading and
writing

Logic mastery makes the hard, easier. Logic mastery  leads to better, stronger and richer comprehension.  Logic mastery  improves reading and writing.  Logic mastery ease learning difficulties.  Logic mastery gives a headstart.  In sum, logic mastery  will develops critical thinking, improve reading and writing, and give a firmer base for work and studies at many levels. Good luck.


After logic  (a) continue reading Three Skills for Algebra, chapters 8 to 14  and do so alongside site area on solving liinear Equations ; or (b) see this calculus starter lesson and Volume 3, Why Slopes  & More Math, chapters 2 to 6;

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Caution: Site advice is approximately correct, for some circumstances, not all. That leaves room for thought

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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.


Try the Twiddla Whiteboard. In principle, it  allows to people to draw and chat together online on a copy of this webpage or a clean sheet. The chat may be via text or audio.  Visit www.twiddla.com to set up whiteboards to work with the webpage of your choice.

For online automated help in senior high school maths & calculus, visit  quickmath.com  For Automatic Calculus and Algebra Help with derivatives, integrals, graphs, linear equations, matrix algebra, visit calc101.com  With  overlap, each site quickmath & calc101offers a different range of services, some free, some not, all based on webmathematica. Good luck.

Chapter 3. Slope Sign Analysis

[Play Video]  2¼ minutes:  Slope Interpretation for a 2D ski hill y = f(x).  (Appeared earlier)

Recapitulation (Some Repetition)

From the slope of her ski, Barbara can say whether her height h(x) is increasing, decreasing or remaining constant.

Remember from the changes in the slope sign, she can locate the high points (local maximums) and low points (local minimums). As she passes over a high point or through a low point, the slope of her ski may be zero. That is, it may become momentarily horizontal as she makes the transition at the top from going up to going down, or vice-versa. In summary, the following can be said, and needs to be remembered.

     

  • From the slope of her ski, Barbara can feel if she is moving uphill, downhill or horizontally but she cannot feel how high she is.
  • As she passes over a hill top, the slope of her ski goes from positive (+ve) to (-ve). Momentarily at the top, the ski will be horizontally and the slope value will pass through 0.
  • As she passes through the low point of a depression, the slope of her ski changes from negative (-ve) to positive (+ve). Momentarily at the bottom, the ski slope may pass through the value 0.

A First Example

Describe the up-down behavior of the height function y = h(x) given the information (recorded by Barbara) in the following line diagram. It shows the sign of the slope m = g(x) = h¢(x) in different intervals.

Solution.   The slope is negative, and therefore the height should be decreasing and the motion downhill between

     

  • between x1 and x2, and also
  • between x2 and x3.
The slope is positive, and therefore the height should be increasing and the motion uphill between

     

  • between x0 and x1,
  • between x3 and x4, and
  • between x5 and x6.
The slope is zero, and the height expected to be constant, and the motion expected to be horizontal,
  • between x4 and x5.

The two words should indicate an expectation based on our physical senses or experience, but not on mathematical considerations. The mathematical theorem justifying this expectation relies only on arithmetic-based definitions and considerations. The slope is also zero at the following points: x1,x2,x3,x4, and x5. The slope at the end points x0 and x6 is unknown.

The next diagram summarize our information about the hills y = h(x).

The arrows show where the height is increasing, decreasing or constant, but not the values of the height. Here


means or signals uphill motion or increasing height,
means or signals downhill motion or decreasing height), and
means or signals horizontal motion or constant height,

From the identification of the intervals where the slope is positive or negative, that is where the skier Barbara went up and down hill, there is enough information to locate the high and low points (hill tops and depression bottoms) on the trail:

     

  1. There is a high point or local maximum at x1.
  2. There is a low point or local minimum at x3.
  3. There is a left end-point low-point at x0
  4. There is a right end-point high point at x6

The Height is Uncertain

To show the height is not determined by sign analysis, the following diagrams sketch two simple trails with the same the slope sign behavior as above, but different heights.

The magnitude or steepness of the slope and not just its sign determines the shape of a curve y = h(x).

A Change in Notation

Instead of using h(x) in the previous pages, we could have used f(x). Instead of using m = g(x) = h¢(x), we could have written f¢(x). What notation is used is less important than the role the notation takes in describing ideas.


y = h(x)
Height
Function
  y = f(x)
Some
Function
   
m = g(x)
Slope
Function
for h(x)
   m = f¢(x)
First
Derivative
for f(x)

As in a play, a given role can be assumed by one of many actors, unless a important star is involved. Second derivatives will appear later.

www.whyslopes.com
Volume 3,  Why Slopes and More Math
- Preview, starter & further lessons for calculus to ease or avoid algebra shock in instruction & self-instruction

Foreword, One Calculus  preview and Online Chapters: (V) signals video (RealPlayer Format)  to watchChapters 2 to 6: offer a very simple preview of calculus and a context for earlier study of  slopes and factored polynomials 

Area Entrance & Hub
Foreword
Chapter Descriptions
1. Introduction
2. Calculus Starter Lesson
2. Second Preview Begins
2 Skier in Motion (V)
2 The Skier (V)
2. Position Dependent (V)
3 Slope & Extrema (V)
4 Single Factor Analysis (V)
4 Two Factor (V)
4 More Factors (V)
4 With Divisors (V)
5 Maxima & Minima Tests
6 Jumps & Discontinuities
8 Review  (optional)
9 On Calculus Studies
11 Slope of Slope
13  Acceleration
14 Limits & Error Control (V)
14 Limit of a Fn.
14. Limited Error Control
14 Signif. Digits
14 Cauchy Limits
14 Sequence Limits
14 Decimal Arith.
15 What is Slope (V)
15 Slope Calculation (V)
15 Slope, a Limit
15 Tangent Lines
15 Linear Approx.,
15 Limits via Algebra (V)
15 Recap.
PS.Chain Rule for Polys
PS Chain Rule- General  (V) -
PS More Chain Rule (V)
PS - Sign Analysis (V)
16 What is Velocity
17  What is Area
18 Integration
18 Area Calculation
18  Fn DefN, 6 Ways
19 Logs & Powers
19 Natural Log.
19 Exponential Fn.
20 What's Next
21 Add Vectors
22 Complex #'s
23 Complex #'s
23 Trig Identity
23 Proofs of.
24 Complex Logs etc

Units in Calculations:
7 Velocity
7 Varying Velocity Example
7. Velocity Calculation
7 Changing Units
7 Same Velocity  Motions
10 Slopes without Units.
10 Units & Slopes
10  Units in Cost vs. Quantity
10  How Units  Appear
10 Unit  Elimination
10 Partial Elimination
10 Interest & Units
12 More on Units
Content Guide

Enriched material: The Appendices of Volume 3 are located in the Real  Analysis  Area.

Pigeon Hole Principle
Constant Difference Thm
Continuous Functions
Rational Functions
Mean Value Theorem
One Side Range Theorem
Range On One Side Theorem
Integration & Lipschitz
 Continuity


These appendices continue the
decimal viewpoint of limits, error
control and continuity begun
in Chapter 14. The One Sided
 Range Theorem
is a postscript,
not in printed version.



Online Volume 2, Three Skills for Algebra, Chapters 1 to 25 - skip 18., verbalizes and explains key skills and concepts, those needed in calculus, again to make the hard easier. A visual understanding of complex numbers may help - serve as back ground info,  in partial fraction decomposition.

 

 


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