# Quod Erat Demonstrandum

## 2010/11/26

### 純量與向量

Filed under: NSS,Physics — johnmayhk @ 12:38 下午

＂All physical quantities can be classified into two types: scalars and vectors. For example, distance, temperature and area are examples of scalars as they can be represented by a real number only, while displacement, velocity and force are examples of vectors as they possess direction as well.＂

## 2010/11/25

### 弧度

Filed under: NSS — johnmayhk @ 12:40 下午
Tags: , $s = r\theta$ $\theta$ is measured in radian） $180^o = \pi$ radian $\pi r = r \theta$ (more…)

## 2010/11/24

### 成正比

Filed under: NSS — johnmayhk @ 3:06 下午

## 2010/11/22

### 小數定律？

Filed under: Fun — johnmayhk @ 5:41 下午 $(x + y)^3 = x^3 + y^3 + 3xy(x + y)(x^2 + xy + y^2)^0$ $(x + y)^5 = x^5 + y^5 + 5xy(x + y)(x^2 + xy + y^2)^1$
(more…)

## 2010/11/20

### 唔打：唯一解與delta非零

Filed under: HKALE,NSS,Pure Mathematics — johnmayhk @ 5:56 下午

## 2010/11/18

### 唔打：矩陣簡單例子

Filed under: Pure Mathematics — johnmayhk @ 11:17 下午

## 2010/11/17

### 證明 Euler’s formula

Filed under: Junior Form Mathematics,University Mathematics — johnmayhk @ 3:10 下午 $V - E + F = 2$

http://www.ics.uci.edu/~eppstein/junkyard/euler/

## 2010/11/14

### Infinite Escher

Filed under: Fun — johnmayhk @ 5:48 下午

This film was created in 1990 by the Sony HDVS Soft Center to demonstrate the nascent High Definition Video technology.

Infinite Escher is a paean to German mathematician and artist MC Escher.

## 2010/11/13

### 精采的做碎形方法

Filed under: Fun — johnmayhk @ 10:02 上午

## 2010/11/12

### 99 現象

Filed under: Fun,Junior Form Mathematics — johnmayhk @ 4:10 下午
Tags: , $\frac{1}{3} = 0.\overline{3}$ $\frac{1}{7} = 0.\overline{142857}$ $0.\overline{3}$ 的 period = 1； $0.\overline{142857}$ 的 period = 6。

## 2010/11/11

### 舊計算機

Filed under: Fun — johnmayhk @ 10:28 上午 http://englishrussia.com/index.php/2007/02/14/72-old-soviet-calculators/

## 2010/11/10

### 有解條件

Filed under: HKALE,Pure Mathematics — johnmayhk @ 3:10 下午 $p,q$ 為常數，問在什麼條件下 $px = q$ 有解？ (more…)

### 答客問：四元數

Filed under: Pure Mathematics — johnmayhk @ 2:27 下午

E : $x^2 + 1 = 0$

## 2010/11/09

### [FW] 他是天才 摺紙數學大師

Filed under: Fun — johnmayhk @ 11:06 下午
Tags:

## 2010/11/05

### 找二次方程

Filed under: NSS — johnmayhk @ 12:05 下午 $x = \frac{1}{y}$，代入 (more…)