Quod Erat Demonstrandum

2010/05/31

兩名美國數學家在五月相繼離世

Filed under: Report — johnmayhk @ 11:12 下午

Martin Gardner(October 21, 1914 – May 22, 2010)
http://en.wikipedia.org/wiki/Martin_Gardner

Walter Rudin(May 2, 1921 – May 20, 2010)
http://en.wikipedia.org/wiki/Walter_Rudin

2010/05/28

[FW][YouTube] 學校教育扼殺了創意嗎?

Filed under: Report — johnmayhk @ 12:48 下午

2010/05/27

[FW] 丘成桐:從明治維新到二戰前後中日數學人才培養之比較

Filed under: Report,University Mathematics — johnmayhk @ 6:10 下午
Tags:

May be an interesting article, just post the links for reference.

Text on 科學網 (2010-02-03)
http://news.sciencenet.cn/htmlnews/2010/2/228034.shtm?id=228034

PDF file from 科學時報
http://paper.sciencenet.cn/dz/upload/20102223646571.pdf

just answer a textbook question from my student

Filed under: Additional / Applied Mathematics,HKALE — johnmayhk @ 12:45 下午
Tags: ,

To Lau (my student)

This is the question you’d asked

“A man lives at A and works at C, and is due at work at 8:30 a.m. He always catches the first train from A to B, which is scheduled to arrive at B at 8:15 a.m. Buses leaves B for C every 20 minutes, and the bus which leaves B at 8:20 a.m. is scheduled to arrive outside the factory at C at 8:27 a.m. The train is, on the average, one minute late and has a standard deviation of 4 minutes. The bus always leaves on time, but is, on the average, 1.5 minutes late with a standard deviation of 2 minutes. The man’s employer leaves home in his car at 8:15 a.m. and the time for his journey has mean value 13 minutes with a standard deviation of 3 minutes. Find the probability that the employer arrives before the employee." (more…)

2010/05/26

無聊一談

Filed under: Life,Report — johnmayhk @ 3:54 下午

港台電視節目:《數碼起義》

第一集《由下而上:新媒體掀起一場革命?》,點擊收看:

http://programme.rthk.org.hk/rthk/tv/programme.php?name=tv/digital&d=2010-05-25&p=4805&e=108782&m=episode

通識是契機,是港生之福(當水用來載舟時)。 (more…)

2010/05/25

[FW] 新數站

Filed under: Information — johnmayhk @ 3:38 下午

比較「新」的一個香港的數學網站,不況看看。

http://www.hkms-nss.net/website/index.php

當中可找到一些香港數學教師的網誌:

http://www.hkms-nss.net/website/link_blog.php

2010/05/24

某詩歌某思緒

Filed under: Life — johnmayhk @ 6:14 下午
Tags: ,

口號、詩詞,無可避免地是簡化了的文字,當中的內容意境,往往要用心體會。

在下是「居無定所」的信徒,在剛過去的主日敬拜中偶遇《因著信》一曲: (more…)

2010/05/22

兩個無言證明

早前網友電郵分享了一個關於海倫公式(Heron’s formula)的「無言證明」(Proof without words)。無言證明者:一看就明,無須多言。

利用兩個引理,得出公式。

引理一K = rs (more…)

2010/05/21

[FW][SONG] 一無所有

Filed under: Fun — johnmayhk @ 10:16 下午
Tags:

「我要給你我的追求,
還有我的自由,
可你卻總是笑我,
一無所有。」


崔健

某一個時代的文化符號。

2010/05/18

四邊形的面積

Filed under: mathematics — johnmayhk @ 9:16 上午
Tags:

四邊形的面積 = \sqrt{(s-a)(s-b)(s-c)(s-d) - \frac{1}{4}(ac+bd+ef)(ac+bd-ef)}

其中,s = \frac{a+b+c+d}{2}(半周界),e,f 為對角線之長度。 (more…)

2010/05/16

空集族

Filed under: Pure Mathematics — johnmayhk @ 11:38 下午
Tags:

同學,先溫習一下兩個集的運算(operations on sets):聯集(union)和交集(intersection)。

舉例,命

A_1 = \{ a,b,c,d \}
A_2 = \{ b,c,d,e \}
A_3 = \{ c,d,e,f \}

則聯集 A_1 \cup A_2 \cup A_3,即三個集的聯合部份是

A_1 \cup A_2 \cup A_3 = \{ a,b,c,d,e,f \} (more…)

2010/05/15

投票站,投注站

Filed under: Uncategorized — johnmayhk @ 12:13 下午

明天的投票站是投注站。大可放下激情,冷靜理性,飲完茶,悠然步入票站,享受閣下之公民權利。朋友同事,相信大部份都不去投票;投的,也會選擇「白姐姐」之類。我沒有爭辯或遊說,只是談到某個位:「民主進程不能一步到位!」我勉強戰競地說:「初中時,我也曾參與爭取『88直選』的活動。」「你可以鬥得贏阿爺咩?啥氣!」嗯,有道理。其實也可以說,事物不一定以「戰鬥」、「對立」的眼光來看。「明知不可為而為」,什麼時候可描述成「愚不可及」?什麼時候可描述成「偉大情操」?也不一定以結果的「成敗得失」計算的。

2010/05/14

我們這一班:F.4D

Filed under: Fun,School Activities — johnmayhk @ 12:19 上午

時間:2010-05-12
地點:濟記某班房
作品: class photo (more…)

2010/05/13

Trivial sharing on trigonometry

Filed under: Additional / Applied Mathematics,mathematics,NSS — johnmayhk @ 7:33 上午
Tags:

What’s wrong with the following steps?

\sin\theta < 0

\Rightarrow \theta lies in the 3rd or 4th quadrant (more…)

2010/05/11

無聊中四數學課紀錄:(1 + 1/n)^n

Filed under: NSS,Teaching — johnmayhk @ 10:57 下午
Tags: ,

為熟習

e = \displaystyle\lim_{n \rightarrow \infty}(1 + \frac{1}{n})^n

上課時,我給同學想想

(a) \displaystyle\lim_{n \rightarrow \infty}(1 + \frac{1}{2n})^{2n} = ? (more…)

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