July 19, 2021July 19, 2021

Complex Numbers are Real

Complex Numbers are Beautiful Too

Real Analysis Study Help for Baby Rudin, Part 1.7

Complex numbers can be represented either using Cartesian coordinates or polar coordinates. The geometric interpretation of complex multiplication is very beautiful using polar coordinates.

Are imaginary numbers real? After all, why are they be called “imaginary”? Doesn’t this name imply that they don’t exist? To

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June 14, 2021July 1, 2021

Existence of nth Roots of Positive Reals

The Completeness Axiom helps us prove the existence of nth roots of positive real numbers, but the proof is quite challenging.

Real Analysis Study Help for Baby Rudin, Part 1.6

The existence of nth roots, including the square root of two, is ultimately based on the continuity of power functions with positive integer exponents. — Ultimately, the continuity of $f(x)=x^{2}$ at $x=\sqrt{2}$ allows us to prove the existence of $\sqrt{2}$ . Later, the argument is based on the Intermediate Value Theorem. In this article, the argument is

f(x)=x^{2} — Ultimately, the continuity of $f(x)=x^{2}$ at $x=\sqrt{2}$ allows us to prove the existence of $\sqrt{2}$ . Later, the argument is based on the Intermediate Value Theorem. In this article, the argument is

… Read the rest

June 7, 2021June 14, 2021

The Archimedean Property

The Completeness Axiom is a sufficient condition to prove the Archimedean Property, but is it necessary?

Real Analysis Study Help for Baby Rudin, Part 1.5

A Visualization of the Archimedean Property in the case where $x=8$ and $y=70$ . The smallest positive integer value of $n$ that makes $nx>y$ is $n=9$ .

x=8 — A Visualization of the Archimedean Property in the case where $x=8$ and $y=70$ . The smallest positive integer value of $n$ that makes $nx>y$ is $n=9$ .

Does the sequence $\left(\frac{1}{n}\right)_{n=1}^{\infty}$ approach zero as $n\rightarrow \infty$ ? Sure! After all, given any number

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April 1, 2021May 7, 2021

Properties of the Supremum

The supremum and infimum of a bounded set of real numbers have many interesting properties

Study Help for Baby Rudin, Part 1.4

One of the properties of the supremum is that it is additive as a set function on sets of real numbers which are bounded above. — The supremum is additive as a set function on sets of real numbers which are bounded above.

The Completeness Axiom for the real number system is intimately tied to the concept of the supremum of a set of

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February 10, 2021February 10, 2021

Least Upper Bound (Supremum) in an Ordered Set

Suprema and Infima (Sups and Infs) Lie at the Heart of Real Analysis. The Range of Cos(n) is an Interesting Example.

Study Help for Baby Rudin, Part 1.3

For an ordered set $S$ and $M\subseteq S$ which is bounded above, the supremum of $M$ , when it exists in $S$ , is also called the least upper bound of $M$ in $S$ .

Which property separates the

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January 19, 2021June 3, 2021

Definitions of Ordered Set and Ordered Field

And an Ordered Field That Can Be Ordered in More Than One Way

Study Help for Baby Rudin, Part 1.2

A visual for a totally ordered set with three elements. — A graphic representation of the totally ordered set of three points $\left\{a,b,c\right\}$ with $a<b<c$ . The directed line segments are not part of the set. They only indicate the order.

\left\{a,b,c\right\} — A graphic representation of the totally ordered set of three points $\left\{a,b,c\right\}$ with $a<b<c$ . The directed line segments are not part of the set. They only indicate the order.

The set of real numbers $\Bbb{R}$ is more than just a set. As

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January 7, 2021January 24, 2021

Baby Rudin: Let Me Help You Understand It!

The First in a Series of Blog Posts on Baby Rudin

Study Help for Baby Rudin, Part 1.1

Bill Kinney's personal copy of Baby Rudin (Principles of Mathematical Analysis, 3rd edition) — My personal copy of Baby Rudin (Principles of Mathematical Analysis, 3rd edition, by Walter Rudin)

The textbook “Principles of Mathematical Analysis”, by Walter Rudin, is considered a “classic” text on real analysis, the subject that uses rigorous deductive

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February 25, 2020February 25, 2020

The Fundamental Theorem of Calculus

Calculus 2, Lectures 5A through 6 (Videotaped Fall 2016)

The Fundamental Theorem of Calculus implies that the area under the graph of the speed function gives the distance traveled function.

The Fundamental Theorem of Calculus is often split into two forms in textbooks.

These forms are typically called the “First Fundamental Theorem of Calculus” and the “Second Fundamental Theorem of … Read the rest

January 27, 2020January 29, 2020

Integration by Parts (and Linear Motion)

Calculus 2, Lectures 3B through 4 (Videotaped Fall 2016)

Integration by parts is needed to compute the definite integral to find the area under this curve representing the speed of a linear motion. — Integration by parts is needed to compute the definite integral to find the area under this curve representing the speed of a linear motion.

You might say that integration by parts is an “unexpected” or “surprising” method of integration.

While the other main method, integration by substitution, can be thought … Read the rest

January 23, 2020January 23, 2020

Integration by Substitution (Method of Integration)

Calculus 2, Lectures 2A through 3A (Videotaped Fall 2016)

How to visualize integration by substitution for a definite integral. The starting and ending areas are the same. — The integral $\displaystyle\int_{0}^{\sqrt{\pi/2}}2x\cos(x^{2})\, dx$ gets transformed to the integral $\displaystyle\int_{0}^{\pi/2}\cos(u)\, du$ under the substitution $u=x^{2}$ and $du=2xdx$ .

\displaystyle\int_{0}^{\sqrt{\pi/2}}2x\cos(x^{2})\, dx — The integral $\displaystyle\int_{0}^{\sqrt{\pi/2}}2x\cos(x^{2})\, dx$ gets transformed to the integral $\displaystyle\int_{0}^{\pi/2}\cos(u)\, du$ under the substitution $u=x^{2}$ and $du=2xdx$ .

In Calculus 1, the techniques of integration introduced are usually pretty straightforward. In fact, they are usually just memorized as basic facts about antiderivatives.

For Calculus 2, various new integration techniques are introduced, including integration by … Read the rest