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A couple of minor clarifications
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jirilebl committed Jun 8, 2021
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24 changes: 24 additions & 0 deletions TODO
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Possibilities in the long term (possibly next possibly other edition):

* Vol I: Add another example for computing limits using the theorems to
subsection 2.2.2? Perhaps not needed, but might be good.
(thx Manuele Santoprete)

* Vol I: Perhaps be always a bit more explicit with the domain on both
"uniformly continuous" and "Lipschitz"
(thx Manuele Santoprete)

* Vol I: A bit more about Dedekind vs Cauchy completeness?
(thx Manuele Santoprete)

* Vol I/II: Add more names to the theorems/propositions. E.g.
From Manuele Santoprete:
"I think it is good to give names to theorems, since it make it easier to
communicate math. There are several spots where one can give a name to the
theorems. The most important one is Proposition 2.1.10. This is often called
the "Monotone Convergence Theorem". I think at least this name should be
used. Also the min-max theorem is often called extreme value theorem. I
think it makes sense to mention this, since many students are familiar with
the term from calculus. Bartle's book has some very nice names. Another one
is the Cauchy Convergence Criterion (Theorem 2.4.5). There are others as
well, but I did not make a note of them. Moreover, Lemma 2.2.3 sometimes is
called the Comparison Theorem."

* Vol I: Perhaps avoid the whole "well ordering of N" and "induction"
equivalence bit. We could just assume induction as axiom and have well
ordering as a proposition. Might require replacing the exercise 0.3.18
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6 changes: 5 additions & 1 deletion ch-contfunc.tex
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Expand Up @@ -1870,7 +1870,11 @@ \subsection{Uniform continuity}
it only depends on $\epsilon$. The domain of definition
of the function makes a difference now. A function that is not uniformly
continuous on a larger set, may be uniformly continuous when restricted to a
smaller set. Note that $x$ and $c$ are not treated any differently
smaller set.
We will say \emph{uniformly continuous on $X$} to mean that
$f$ restricted to $X$ is uniformly continuous, or perhaps to just emphasize
the domain.
Note that $x$ and $c$ are not treated any differently
in this definition.

\begin{example}
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1 change: 1 addition & 0 deletions ch-real-nums.tex
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Expand Up @@ -546,6 +546,7 @@ \subsection{The set of real numbers}
real number $c$ such that
$a < c < b$. Take, for example, $c = \frac{a+b}{2}$ (why?). In fact,
there are infinitely many real numbers between $a$ and $b$.
We will use this fact in the next example.

The most useful property of $\R$ for analysts
is not just that it is an ordered field, but that it has the
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3 changes: 2 additions & 1 deletion ch-vol1-intro.tex
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Expand Up @@ -120,7 +120,8 @@ \section{About this book}
Jim Brandt, Kenji Kozai, Arthur Busch, Anton Petrunin,
Mark Meilstrup, Harold P.\ Boas, Atilla Y{\i}lmaz,
Thomas Mahoney, Scott Armstrong, and Paul Sacks,
Matthias Weber, Robert Niemeyer, Amanullah Nabavi,
Matthias Weber, Manuele Santoprete,
Robert Niemeyer, Amanullah Nabavi,
for teaching with the book and giving me lots of useful feedback.
Frank Beatrous wrote the University of Pittsburgh version extensions, which
served as inspiration for many more recent additions.
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36 changes: 1 addition & 35 deletions changes-draft.html
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This file is a draft of the new changes for http://www.jirka.org/ra/changes.html

<li>When stating that well ordering of $\mathbb{N}$ and induction are
equivalent, hedge our bets with "in a sense" and add a footnote mentioning
that we are really assuming $n-1$ exists (which is obvious from the proof).
In a related change, make exercise 0.3.18 just straight to the point and
don't mention the equivalence.
<li>Reword the beginning of the proof of Example 1.2.3.
<li>Make Proposition 1.4.1 more readable.
<li>In the proofs of Propositions 2.3.2, 2.3.6, Example 3.1.8, when referring to a sequence, always
use braces.
<li>Add explicit link/reference to chapter 7 to remark 2.4.6.
<li>Add another example restriction on which $g$ is continuous to Example 3.2.13.
<li>Reword Lemma 3.3.1 and Theorem 3.3.2 (min-max) as a simpler single sentence.
<li>Make the Min-max theorem alternatively titled "Extreme value theorem" which
is more common. Emphasize the "closed and bounded" in the theorem
statement.
<li>Reword the proof of Proposition 4.1.10 a little bit to make it clearer.
Also include a tiny bit more motivation.
<li>Add some intuition (being in a fog analogy) to the intro for critical points.
<li>Add Remark 5.1.15 to say something about integral being a sum and being
global as opposed to derivatives being local.
<li>In 5.2 add a few more motivating sentences. And merge the paragraph from
below Proposition 5.2.5 to the one above it to make things flow a little better.
<li>Mark 5.5.13 as "Integral test," and add that to the index.
<li>In 6.3, define "initial condition" as a term.
<li>At the end of 6.3, reword the quip about continuity being necessary and add a
very short remark about Peano existence if $F$ is only
continuous, to justify Example 6.3.6 being discontinuous.
<li>Name the identity bit of Definition 7.1.1 the "identity of
indiscernibles." It is a bit wordy, but it feels like the property ought to
have a name if the others do.
<li>Reword proof of Proposition 7.2.14 to do the forward direction first.
<li>Add $A \subset \overline{A}$ to Proposition 7.2.19 rather than just in text.
The proof flows much nicer then.
<li>Several small clarifications.
<li>A few more explicit references/links.

31 changes: 0 additions & 31 deletions changes2-draft.html
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This file is a draft of the new changes for http://www.jirka.org/ra/changes2.html

<li>On page 11, add a short note about the $d+1$ linearly independent
vectors from the definition of dimension.
<li>In Exercise 8.4.7, assume $q$ is not identically zero. The result is
vacuously true even if $q$ is identically zero, but there is no reason to
make students think about this rather stupid technicality.
<li>The proof in Example 8.1.25 is hopefully clearer.
<li>In definition 8.3.8, remove the definition of the notation $D_j f$. We
never used it later.
<li>In Definition 9.2.1, change the definition of "simple" for non-closed
paths. Typically a path that bites itself back in the middle is not called
simple, so rule out that case.
<li>Rename subsection 10.3.3 to "Images of null sets under differentiable
functions".
<li>In proof of Lemma 10.3.9, say how to prove it for open balls.
<li>Improve definition 10.6.1 to be (much) simpler (though equivalent): Only
take a finite disjoint union of simple closed sets as we are assuming $U$
is bounded anyway.
<li>Reorder the proof of Theorem 10.7.2 a little bit to make it more logical.
<li>On page 148, add a short note that the $e^{z+w}=e^ze^w$ leads to a quick
computation of the power series at any point.
<li>In Corollary 11.3.7, emphasize that that $a$ is any complex number,
since just above it was a real number.
<li>In definition of the exponential on page 147 (the definition of
$E(z)$) explicitly say that this means that it is analytic.
<li>Be more precise in Exercise 11.4.9 to say to derive the power series at the
origin.
<li>In Example 11.6.3, emphasize that $f_n$ are continuous.
<li>In 11.8.2, when saying we could develop everything with sines and
cosines, give the actual form of the series and refer to Euler's formula,
so that when we later call such series also Fourier series, the reader is
not confused.

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