本區搜索:
Yahoo!字典
打印

Tagents to Circles

[隱藏]

Tagents to Circles

唔好意思丫, 又係我丫 我又唔識計啦....

Q21.  我畫到張紙花哂都唔識點prove


Q24.  我試過join 咗 zy 同 zx, 跟住搵angle 搵咗n 耐, 結果都係唔識搵 xy 既length.   答案係..... 3 cm


Q36.a) 我唔係好識prove 野.....

b) 好亂丫

sorry ar, 我知我蠢, 但大家幫下我啦, 聽日test 啦 唔該哂!
附件: 您所在的用戶組無法下載或查看附件
   

TOP

Q21. Prove that angle OCD is a right angle.
  Proof: Consider the angle sum of triangle OCD
  (Hints: total 4 reasons to prove)

Q24. No need to join any lines.
  Use the properties of tangents, and cosine law to find the length of XY.

打住先...
【DSE Maths】中大教育文憑 × 數學系畢業◆助你奪*升Lv~
首次以課題分班,10月開班招生,快d黎睇下~

導師簡介:按此進入

TOP

21) angle BOA = 60 (angle at centre = twice angle at circumference)
=> angle BFO = 90
=>angle OCD =90

24)
附件: 您所在的用戶組無法下載或查看附件

TOP

Q36
a. Construct a line from S to a point on OX such that the line is perpendicular to OX
 Then you can solve it by Pyth. Thm.
b. First, find CA, CB and BA respectively with aid of part a
 Then use the fact that CA = CB + BA
【DSE Maths】中大教育文憑 × 數學系畢業◆助你奪*升Lv~
首次以課題分班,10月開班招生,快d黎睇下~

導師簡介:按此進入

TOP

引用:
原帖由 Simon 於 2011-5-17 12:34 AM 發表
Q36
a. Construct a line from S to a point on OX such that the line is perpendicular to OX
 Then you can solve it by Pyth. Thm.
b. First, find CA, CB and BA respectively with aid of part a
 Then  ...
alternative method
得閒得制既方法


[ 本帖最後由 11AL考生 於 2011-5-17 12:55 AM 編輯 ]
附件: 您所在的用戶組無法下載或查看附件

TOP

by a)

TOP


Part a:
OT = x, ST = y (radii)
OS = x + y
OM = x - y
MS2 = OS2 - OM2
= x^2 + 2xy + y^2 - x^2 + 2xy - y^2
= 4xy
MS = 2 sqrt(xy)
XY = MS = 2 sqrt(xy)

Part b:
By part a, we have
AB = 2 sqrt(ab)
BC = 2 sqrt(bc)
AC = 2 sqrt(ac)

CA = CB + BA
sqrt(ca) = sqrt(cb) + sqrt(ba)
Divide both sides by sqrt(abc)
1 / sqrt(b) = 1 / sqrt(a) + 1 / sqrt(c)
附件: 您所在的用戶組無法下載或查看附件
【DSE Maths】中大教育文憑 × 數學系畢業◆助你奪*升Lv~
首次以課題分班,10月開班招生,快d黎睇下~

導師簡介:按此進入

TOP

唔該哂兩位

TOP

重要聲明:小卒資訊論壇 是一個公開的學術交流及分享平台。 論壇內所有檔案及內容 都只可作學術交流之用,絕不能用商業用途。 所有會員均須對自己所發表的言論而引起的法律責任負責(包括上傳檔案或連結), 本壇並不擔保該等資料之準確性及可靠性,且概不會就因有關資料之任何不確或遺漏而引致之任何損失或 損害承擔任何責任(不論是否與侵權行為、訂立契約或其他方面有關 ) 。