
What Exactly is Dirac’s Delta Function?
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Introduction: "Convenient Notation"In Dirac's Principles of Quantum Mechanics published in 1930 he introduced a "convenient notation" he referred …

Fixing Things Which Can Go Wrong With Complex Numbers
Abstract
This article will build on the hints about treating the complex numbers as a branched surface, briefly described and pictured in section 4.2…

Series in Mathematics: From Zeno to Quantum Theory
Introduction
Series play a decisive role in many branches of mathematics. They accompanied mathematical developments from Zeno of Elea (##5##-th century…

Epsilontic – Limits and Continuity
Abstract
I remember that I had some difficulties moving from school mathematics to university mathematics. From what I read on PF through the years, I…

Differential Equation Systems and Nature
Abstract
"Mathematics is the native language of nature." is a phrase that is often used when it comes to explaining why mathematics is all around in natural…

Beginners Guide to Precalculus, Calculus and Infinitesimals
Introduction
I am convinced students learn Calculus far too late. In my view, there has never been a good reason for this.In the US, they go through…

What Are Numbers?
Introduction
When doing mathematics, we usually take for granted what natural numbers, integers, and rationals are. They are pretty intuitive. Going…

What Are Infinitesimals – Simple Version
Introduction
When I learned calculus, the intuitive idea of infinitesimal was used. These are real numbers so small that, for all practical purposes (say…

What Are Infinitesimals – Advanced Version
Introduction
When I learned calculus, the intuitive idea of infinitesimal was used. These are real numbers so small that, for all practical purposes (say…

The Art of Integration
Abstract
My school teacher used to say
"Everybody can differentiate, but it takes an artist to integrate."
The mathematical reason behind this phrase…

An Overview of Complex Differentiation and Integration
Abstract
I want to shed some light on complex analysis without getting all the technical details in the way which are necessary for the precise treatments…

Reduction of Order For Recursions
This is not meant as a full introduction to recursion relations but it should suffice for just about any level of the student.Most of us remember recursion…

A Novel Technique of Calculating Unit Hypercube Integrals
Introduction
In this insight article, we will build all the machinery necessary to evaluate unit hypercube integrals by a novel technique. We will first…

The Amazing Relationship Between Integration And Euler’s Number
We use integration to measure lengths, areas, or volumes. This is a geometrical interpretation, but we want to examine an analytical interpretation that…

How to Solve Second-Order Partial Derivatives
Introduction
A frequent concern among students is how to carry out higher order partial derivatives where a change of variables and the chain rule are…

The Orin Fractional Calculus
Introduction
This bit is what new thing you can learn reading this:) As for original content, I only have hope that the method of using the sets
$$C_N^n:…

How to Find a Potential Function of a Vector Field
Definition and summary
Given a vector field ##\vec F(x,y,z)## that has a potential function, how do you find it?
Conditions and equations
$$\nabla \phi(x,y,z)…

Real Numbers Explained: Definition, Axioms & Properties
Real numbers are the complete set of values on the continuous number line, denoted ℝ, and they include both rational numbers (fractions and repeating…

What is Integration By Parts? A 5 Minute Introduction
Definition/Summary
In this article, we shall learn a method for integrating the product of two functions. This method is derived from the 'product rule'…

What Is a Limit of a Function? Definition, Laws & Examples
A limit describes the value a function or sequence approaches as its input gets arbitrarily close to a specific point, without requiring the function to…

Demystifying Parameterization and Surface Integrals
Introduction
This article will attempt to take the mystery out of setting up surface integrals. It will explain the basic ideas underlying surface integration…

Fundamental Theorem of Calculus: An Intuitive Numerical View
The fundamental theorem of calculus states that integration and differentiation are reverse operations of one another. This article gives an intuitive,…

Learn the Basics of Hilbert Spaces and Their Relatives: Operators
Operators. The Maze Of Definitions.
We will use the conventions of part I (Basics), which are ##\mathbb{F}\in \{\mathbb{R},\mathbb{C}\}##,…

Learn the Basics of Hilbert Spaces and Their Relatives: Definitions
Basics
Language first: There is no such thing as the Hilbert space.Hilbert spaces can look rather different, and which one is used in…

Demystifying the Chain Rule in Calculus
Introduction
There are a number of posts on PF involving a general confusion over the multi-variable chain rule. The problem is often caused by…

Learn Further Sums Found Through Fourier Series
In an earlier insight, I looked at the Fourier series for some simple polynomials and what we could deduce from those series. There is a lot more to be…

Learn an Integral Result from Parseval’s Theorem
Introduction:
In this Insight article, Parseval's theorem will be applied to a sinusoidal signal that lasts a finite period of time. It will be shown…

The Pantheon of Derivatives – Important Theorems (V)
Implicit Function Theorem [1]
Jacobi Matrix (Chain Rule).
Let ## (x_0,y_0 ) ## be a point in$$U_1 \times U_2 = \{x \in \mathbb{R}^k\,\vert \,||x-x_0||<…

The Pantheon of Derivatives – Manifolds And Vector Fields (II)
Generalizations Beyond ##\mathbb{R}## and ##\mathbb{C}##
As mentioned in the section on complex functions (The Pantheon of Derivatives - Part…

The Pantheon of Derivatives – The Direction (I)
Differentiation in a Nutshell
I want to gather the various concepts in one place, to reveal the similarities between them, as they are often…

Trick to Solving Integrals Involving Tangent and Secant
This little trick is used for some integration problems involving trigonometric functions is probably well-known, but I only learned it yesterday. So…

Using the Fourier Series To Find Some Interesting Sums
Preliminaries
If f(x) is periodic with period 2p and f’(x) exists and is finite for -π<x<π, then f can be written as a Fourier series:
[itex]f(x)=\sum_{n=-\infty}^{\infty}a_{n}e^{inx}…

Learn Partial Differentiation Without Tears
Differentiation is usually taught quite well. Perhaps that's because it is the first introduction to calculus, which is considered a big step in a student's…

The Gauge Integral: Why Henstock–Kurzweil Deserves a Course
The gauge integral, also called the Henstock–Kurzweil integral, is a modification of the Riemann integral that replaces a single fixed tolerance with…

The Calculus Paradox: Why ∫1/x dx Can Equal 1 = 0
The paradox where integration seems to prove 1 = 0 arises from treating an indefinite integral as a single function instead of a set of antiderivatives.…

Self-Study Analysis: Metric Spaces, Measure Theory & More
Direct answer: After finishing analysis on real numbers and n-dimensional real space, the recommended path for self-study is Carothers' Real Analysis for…

Self-Study Analysis: A Proof-to-Manifolds Roadmap
Direct answer: To self-study real analysis from a calculus background, follow this sequence: complete a proof-writing book (Velleman's How to Prove It…

Hear the Case for Learning Complex Math
Resistance to complex math seems to never die out. I see it frequently in PF posts. Often it takes the form of challenges rather than questions. …

Complex Number Paradoxes Explained: Why Exponent Rules Fail
Complex exponentiation breaks the familiar high-school rules for powers because those rules — (x^a)^b = x^ab, (xy)^a = x^a y^a, and x^a = x^b ⇒ a =…

How to Solve Nonhomogeneous Linear ODEs using Annihilators
My previous Insights article, Solving Homogeneous Linear ODEs using Annihilators, discussed several examples of homogeneous differential equations, equations…

Solving Homogeneous Linear ODEs using Annihilators
In this Insights article we'll look at a limited class of ordinary differential equations -- homogeneous linear ODES with constant coefficients. Although…

Why 1 = 0.999…: Four Simple Proofs Explained
Yes, 1 and 0.999... are exactly the same real number, not merely two numbers that happen to be extremely close. This surprises many people because 0.999...…

Proofs in Mathematics: Methods, Examples, and How to Write Them
A mathematical proof is a logical argument, built only from definitions, axioms, and previously established results, that shows a statement is true in…

Cardinal and Ordinal Numbers: An Informal Introduction
Cardinal numbers measure the size of a set, including infinite sets, while ordinal numbers describe the structure of a well-ordered set. Every set can…

Infinity in Mathematics: What It Really Means, Explained
Infinity is not a real number but a set of distinct mathematical tools, including the extended real line, the projective real line, the Riemann sphere,…

Is 1 Equal to 0.999…? Rigorous Proof Explained
Yes, 1 equals 0.999... exactly, not approximately. This is a proven mathematical fact once the notation 0.999... and the concept of an infinite sum are…

Nowhere Differentiable Functions: Fejér Kernel & Cesàro Sums
This is Part 2 of a series of articles in which the goal is to exhibit a continuous function that is nowhere differentiable and to explore some interesting…

Constructing a Continuous but Nowhere Differentiable Function
When studying calculus, we learn that every differentiable function is continuous, but a continuous function need not be differentiable at every point.…
