# Ideal in Ring

** Historical Background**:

**Ideal (理想)** was a by-product by mathematicians in the 350-year proof of the 17CE Fermat’s Last Theorem, wherein they found a violation of the existing “Fundemental Law of Arithmetic” (Unique Prime Factorization) . Since it is a Law, there must be an alternative * ideal* number to satisfy it, hence the birth of the “Ideal”.

Read here: the raison d’être of Ideal : **What is an Ideal ?**

**Note**:

Why Integer (Z) is called “Ring” (Dedekind coined it using the German word “Der Ring”) ? because

{1, 2, … , 11, 12 = 0} is clock number “Z/12Z” like a Ring-shaped Clock 🕜

** Application**:

The ancient “Chinese Remainder Theorem” (aka 韩信点兵 ) since 200 BCE is explained by 19CE Ideal Theory.

[**Solve**] : “The Problem of 6 Professors”

Ideal= “Whateverinsidemultipliesoutside, still comes backinside.”

…

**Ring Examples:**

- Integers Z
- Polynomial with coefficients in Real number , or Complex number, or
**Matrix**(yes!) - Infinite Ring
- Finite Ring (Z/nZ )
- Z/pZ = Field (p is prime)

**Reference**:

33 short videos on the scariest Math subject in universities (France, USA, China, Singapore,… ) “Abstract Algebra” made simple by this charming lecturer.

# What makes a good Conjecture?

If you can’t prove, then makes an outrageous conjecture!

Examples:

- Fermat’s Last Theorem (Conjecture for 380 years until proven as “Theorem” in 1994)
- Poincare “Conjecture” = (Theorem proven by Grigoli Perelman )
- Goldbach’s Conjecture (best proof by 陈景润 “1+2”)
- Yang-Mills Conjecture (7 Millennia Clay-Prize Problems)
- Collatz Conjecture

https://www.quantamagazine.org/the-subtle-art-of-the-mathematical-conjecture-20190507/

# Without Leap Year 29/2, Winter would become Summer

# Golden Ratio

# Music = Math + History

To really appreciate music, you must understand this Math & history :

5 notes to 7 notes to 12 notes.

& fractions: 3/2, 3/4, 2/1 (octave)

Music = Math + History

1. Ancient China 600 BC 管仲 (5 notes 宫商角徵\zhǐ羽）

2. Pythagoras 450 BC (7 notes, Chords 和弦)

3. Modern Music: 十二平均律 (明朝 1600 AD 朱载堉- > Bach 1700 AD)

Pythagoras did not believe in Irrational numbers (sqroot 2) , so only 7 integer notes.

17CE Chinese 明朝 Prince invented 12 notes music, using a giant 81-row Abacus to compute the12th root of 2 (picture below) ：

https://chinoiseries2014.wordpress.com/2019/02/07/%e5%8d%81%e4%ba%8c%e5%b9%b3%e5%9d%87%e7%8e%87/

# Fourier Transformation in Data Science

Data Science =

Math (Fourier FFT) +

AI (Convoluted Neural Network) +

Big Data

https://www.kdnuggets.com/2020/02/fourier-transformation-data-scientist.html