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Analysis

dirac function

What Exactly is Dirac’s Delta Function?

August 29, 2025
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0 Comments
Introduction: "Convenient Notation"In Dirac's Principles of Quantum Mechanics published in 1930 he introduced a "convenient notation" he referred …
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complex numbers

Fixing Things Which Can Go Wrong With Complex Numbers

July 20, 2025
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0 Comments
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…
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geometric series

Series in Mathematics: From Zeno to Quantum Theory

November 7, 2023
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2 Comments
Introduction Series play a decisive role in many branches of mathematics. They accompanied mathematical developments from Zeno of Elea (##5##-th century…
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Epsilontic limits and continuity

Epsilontic – Limits and Continuity

October 6, 2023
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1 Comment
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…
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Differential Equation Systems and Nature

Differential Equation Systems and Nature

August 27, 2023
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12 Comments
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…
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calc precalc

Beginners Guide to Precalculus, Calculus and Infinitesimals

August 18, 2023
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3 Comments
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…
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what are numbers

What Are Numbers?

August 14, 2023
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7 Comments
Introduction When doing mathematics,  we usually take for granted what natural numbers, integers, and rationals are. They are pretty intuitive.   Going…
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Infinitesimals

What Are Infinitesimals – Simple Version

June 4, 2023
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5 Comments
Introduction When I learned calculus, the intuitive idea of infinitesimal was used. These are real numbers so small that, for all practical purposes (say…
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Infinitesimals

What Are Infinitesimals – Advanced Version

May 24, 2023
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0 Comments
Introduction When I learned calculus, the intuitive idea of infinitesimal was used. These are real numbers so small that, for all practical purposes (say…
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art of integration

The Art of Integration

April 10, 2023
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0 Comments
Abstract My school teacher used to say "Everybody can differentiate, but it takes an artist to integrate." The mathematical reason behind this phrase…
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integration and complex differentiation

An Overview of Complex Differentiation and Integration

March 14, 2023
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0 Comments
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…
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recursion

Reduction of Order For Recursions

October 4, 2022
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0 Comments
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…
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hypercube integral

A Novel Technique of Calculating Unit Hypercube Integrals

April 14, 2022
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1 Comment
Introduction In this insight article, we will build all the machinery necessary to evaluate unit hypercube integrals by a novel technique. We will first…
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Hyperbola

The Amazing Relationship Between Integration And Euler’s Number

March 28, 2022
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0 Comments
We use integration to measure lengths, areas, or volumes. This is a geometrical interpretation, but we want to examine an analytical interpretation that…
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calculus

How to Solve Second-Order Partial Derivatives

May 19, 2020
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1 Comment
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…
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Integral Representations of Some Special Functions

The Orin Fractional Calculus

March 23, 2020
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8 Comments
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:…
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How to Find Potential Functions

How to Find a Potential Function of a Vector Field

June 18, 2019
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0 Comments
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)…
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What are real numbers

Real Numbers: Definition, Properties & Completeness

May 22, 2019
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0 Comments
Definition of real numbers Real numbers are the set of all values that can appear on the continuous number line. They include rational numbers (fractions…
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integration by parts

What is Integration By Parts? A 5 Minute Introduction

May 11, 2019
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0 Comments
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'…
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Limit of a Function

Limits of Functions for Calculus: Definition & Examples

April 17, 2019
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0 Comments
What is a limit? In mathematics, a limit describes the behavior of a function or sequence as its input approaches a particular value. Limits are a cornerstone…
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surface integral

Demystifying Parameterization and Surface Integrals

April 13, 2019
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3 Comments
Introduction This article will attempt to take the mystery out of setting up surface integrals. It will explain the basic ideas underlying surface integration…
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Calculus Therom

A Numerical Insight for the Fundamental Theorem of Calculus

November 8, 2018
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9 Comments
The purpose of this article is not to provide some rigorous statement, neither a rigorous clever proof of the fundamental theorem of calculus. It is rather…
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hilbertspaces2

Learn the Basics of Hilbert Spaces and Their Relatives: Operators

March 6, 2018
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4 Comments
  Operators. The Maze Of Definitions. We will use the conventions of part I (Basics), which are ##\mathbb{F}\in \{\mathbb{R},\mathbb{C}\}##,…
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hilbertspaces

Learn the Basics of Hilbert Spaces and Their Relatives: Definitions

February 16, 2018
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2 Comments
  Basics Language first: There is no such thing as the Hilbert space.Hilbert spaces can look rather different, and which one is used in…
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Demystifying the Chain Rule in Calculus

January 2, 2018
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7 Comments
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…
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fourierseries2

Learn Further Sums Found Through Fourier Series

September 28, 2017
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5 Comments
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…
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Parsevalstheorem

Learn an Integral Result from Parseval’s Theorem

July 12, 2017
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5 Comments
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…
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deriitive5

The Pantheon of Derivatives – Important Theorems (V)

March 25, 2017
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2 Comments
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||<…
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deriitive2

The Pantheon of Derivatives – Manifolds And Vector Fields (II)

March 17, 2017
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8 Comments
  Generalizations Beyond ##\mathbb{R}## and ##\mathbb{C}## As mentioned in the section on complex functions (The Pantheon of Derivatives - Part…
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deriitive

The Pantheon of Derivatives – The Direction (I)

March 16, 2017
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3 Comments
  Differentiation in a Nutshell I want to gather the various concepts in one place, to reveal the similarities between them, as they are often…
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integraltrick

Trick to Solving Integrals Involving Tangent and Secant

March 6, 2017
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6 Comments
This little trick is used for some integration problems involving trigonometric functions is probably well-known, but I only learned it yesterday. So…
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FourierSeries

Using the Fourier Series To Find Some Interesting Sums

December 22, 2016
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4 Comments
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}…
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partial-differentiation

Learn Partial Differentiation Without Tears

October 21, 2016
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6 Comments
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…
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omissionguage

Why the Gauge (Henstock-Kurzweil) Integral Matters

July 22, 2016
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31 Comments
The gauge integral (Henstock–Kurzweil) The current (pure) mathematics curriculum at the university is well-established. Most of the choices made are…
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integralmisconceptions

Integration Paradoxes: Indefinite Integrals and Constants

July 3, 2016
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40 Comments
Introduction Integration is an incredibly useful technique taught in all calculus classes. Nevertheless, there are certain paradoxes involved with integration…
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selfstudyanalysis

Advanced Real Analysis: Measure & Functional Study Plan

May 1, 2016
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14 Comments
Prerequisites If you wish to follow this guide, you should be familiar with analysis on ##\mathbb{R}## and ##\mathbb{R}^n##. See my previous insight for…
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mathanalysis1

Self-Study Analysis Roadmap: From Proofs to Manifolds

March 5, 2016
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26 Comments
Introduction This is a sequel to my posts on self-studying mathematics. I have already given a very detailed road map on how to study high school mathematics…
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complexmath

Hear the Case for Learning Complex Math

February 3, 2016
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15 Comments
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. …
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complexnumbers

Things Which Can Go Wrong with Complex Numbers

January 14, 2016
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3 Comments
At the first sight, there are many paradoxes in complex number theory. Here are some nice examples of things that don't seem to work:Example A [itex]-1=i^2=\sqrt{-1}\cdot\sqrt{-1}=\sqrt{(-1)(-1)}=\sqrt{1}=1[/itex]Example…
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ODE2

How to Solve Nonhomogeneous Linear ODEs using Annihilators

December 9, 2015
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3 Comments
My previous Insights article, Solving Homogeneous Linear ODEs using Annihilators, discussed several examples of homogeneous differential equations, equations…
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ODE1

Solving Homogeneous Linear ODEs using Annihilators

December 7, 2015
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8 Comments
In this Insights article we'll look at a limited class of ordinary differential equations -- homogeneous linear ODES with constant coefficients. Although…
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999equals1

Why 1 Equals 0.999… — Explanations & Rigorous Proofs

October 17, 2015
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111 Comments
Why do people say 1 and 0.999... are equal? Aren't they two different numbers? No — 1 and 0.999... really are the same number, although that can feel…
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proofs

Mathematical Proofs: How to Understand and Write Them

September 22, 2015
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28 Comments
Introduction This FAQ is about proofs. Proofs are central to mathematics, and writing proofs is a skill many people find hard to master. There are two…
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cardinalnumbers

Informal Introduction to Cardinal Numbers

September 13, 2015
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1 Comment
Cardinal numbers We will now give an informal introduction to cardinal numbers. We will later formalize this by using ordinal numbers. Informally, cardinal…
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infinity_faq

Infinity in Mathematics: Limits and Cardinality FAQ

September 2, 2015
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17 Comments
Introduction Understanding the behavior of infinity is one of the major accomplishments of mathematics. However, the infinite is often misunderstood and…
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999

Rigorous Proof: Why 0.999… Equals 1 (Geometric Series)

August 30, 2015
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101 Comments
Yes. What 0.999... Means First, we have not addressed what 0.999... means. So it is best to first describe what the notation [tex]b_0.b_1b_2b_3...[/tex]…
https://www.physicsforums.com/insights/wp-content/uploads/2015/08/999.png 135 240 Micromass https://www.physicsforums.com/insights/wp-content/uploads/2019/02/Physics_Forums_Insights_logo.png Micromass2015-08-30 22:24:542026-01-24 07:28:37Rigorous Proof: Why 0.999… Equals 1 (Geometric Series)
differentiable function 2

Nowhere Differentiable Functions: Fejér Kernel & Cesàro Sums

May 7, 2015
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2 Comments
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…
https://www.physicsforums.com/insights/wp-content/uploads/2015/05/cont-funt-tut2.png 135 240 jbunniii https://www.physicsforums.com/insights/wp-content/uploads/2019/02/Physics_Forums_Insights_logo.png jbunniii2015-05-07 02:37:212026-07-27 14:11:21Nowhere Differentiable Functions: Fejér Kernel & Cesàro Sums
differentiable function

Constructing a Continuous but Nowhere Differentiable Function

May 2, 2015
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11 Comments
When studying calculus, we learn that every differentiable function is continuous, but a continuous function need not be differentiable at every point.…
https://www.physicsforums.com/insights/wp-content/uploads/2015/05/cont-funt-tut.png 135 240 jbunniii https://www.physicsforums.com/insights/wp-content/uploads/2019/02/Physics_Forums_Insights_logo.png jbunniii2015-05-02 16:26:232026-07-27 14:11:11Constructing a Continuous but Nowhere Differentiable Function

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