# Quod Erat Demonstrandum

## 2009/04/29

### 純數小技

Filed under: HKALE,Pure Mathematics — johnmayhk @ 5:53 下午
Tags:

$\frac{d}{dx}e^{\sin x}$

## 2009/04/28

### 有關圓形方程和軌跡的無聊討論

Filed under: HKCEE,mathematics — johnmayhk @ 4:28 下午
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【其一】 上課材料

To 4E students: you may download the worksheet (2009-04-24) at

f4-additional-mathematics-worksheet-20090424

together with some exploration at

http://www.hkedcity.net/ihouse_tools/forum/read.phtml?forum_id=27877&current_page=&i=1247383&t=1247383

【其二】 笑到喊

$x^2 + y^2 + Dx + Ey + F = 0$ – – – – – – (*)

$x^4 + 2x^3 + (2y^2 - 2y - 1)x^2 + (2y^2 - 2y - 2)x + y^4 - 2y^3 - y^2 + 2y + 1 = 0$

## 2009/04/27

### [FW][YouTube] 我阿媽係外星人 My mom is an alien

Filed under: Fun — johnmayhk @ 10:01 下午

### 2009 CE Mathematics Paper

Filed under: HKCEE,mathematics — johnmayhk @ 3:38 下午

2009 CE Mathematics Paper I Q.17

Given

A, B, C and D lie on the horizontal ground. CE is perpendicular to the plane ABE.
AC = 28 cm, BC = 25 cm, BD = 6 cm, BE = 24 cm, $\angle$ABC = 57$^o$.

Find the shortest distance from E to the horizontal ground. (more…)

## 2009/04/22

### 中二數學：累積頻數曲線

Filed under: Junior Form Mathematics — johnmayhk @ 6:10 下午

1.

2. (more…)

### 一些有關不能使用 l’Hôpital’s rule 的例子

Filed under: HKALE,Pure Mathematics — johnmayhk @ 9:31 上午
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## 2009/04/21

### Trivial reflection of mathematics teaching

Filed under: HKALE,Pure Mathematics — johnmayhk @ 6:04 下午
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Pure Mathematics is a subject of mathematical “techniques". It provides students with certain tools and procedures to solve certain mathematical problems.

However, for me, Pure Mathematics is a subject of “art".

“Techniques" can be taught, while “art" cannot be taught easily. (more…)

## 2009/04/20

### Just reply to my so-called ETV

Filed under: Fun,Junior Form Mathematics — johnmayhk @ 12:45 上午

Here is just a reply to my primary school mathematics ETV (magic square).

When I was a primary school boy, my mathematics teacher taught us how to construct magic square, today, I still remember what she had taught me. For your reference, here is an easy way to construct magic square of odd order:

http://en.wikipedia.org/wiki/Magic_square#A_method_for_constructing_a_magic_square_of_odd_order

Students, try to construct magic squares (more…)

## 2009/04/19

### 等我教下小學數啦

Filed under: Fun — johnmayhk @ 12:11 上午

1. 圓周率

## 2009/04/17

### 可導性

Filed under: HKALE,Pure Mathematics — johnmayhk @ 5:23 下午
Tags: , ,

1. Put $x = 0$ into the expression of $f'(x)$ and it is undefined, then $f(x)$ is not differentiable at $x = 0$. True?
2. If $\lim_{x \rightarrow 0^-}f'(x) = \lim_{x \rightarrow 0^+}f'(x)$, then $f(x)$ is differentiable at $x = 0$. True?
3. If $\lim_{x \rightarrow 0^-}f'(x)$ is finite, then the value of $\lim_{h \rightarrow 0^-}\frac{f(h) - f(0)}{h}$ is also finite. True? (more…)

## 2009/04/15

### 純數生活例子（無聊篇）

Filed under: Pure Mathematics — johnmayhk @ 8:09 上午

## 2009/04/14

### 家庭小片段-0009

Filed under: Family,Life — johnmayhk @ 2:13 上午

## 2009/04/08

### 電腦，對你又愛又恨。

Filed under: Family,Life — johnmayhk @ 9:58 下午

## 2009/04/01

### [FW] 網絡民主 01.04.2009

Filed under: Life — johnmayhk @ 12:12 下午

### Discussion of F.4 General Mathematics Test Paper (2009-03-26)

Filed under: HKCEE,mathematics — johnmayhk @ 9:22 上午
Tags:

To F.4E students

Please visit my forum and do some exploration on some easy geometry questions in the previous quiz by clicking the following.

http://www.hkedcity.net/ihouse_tools/forum/read.phtml?forum_id=27877&current_page=&i=1247268&t=1247268