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... 作者: 11AL考生 時間: 2011-5-17 12:08 AM
21) angle BOA = 60 (angle at centre = twice angle at circumference)
=> angle BFO = 90
=>angle OCD =90
24)
[attach]33871[/attach] 作者: Simon 時間: 2011-5-17 12:34 AM
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 作者: 11AL考生 時間: 2011-5-17 12:43 AM
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
[attach]33872[/attach]
[ 本帖最後由 11AL考生 於 2011-5-17 12:55 AM 編輯 ] 作者: 11AL考生 時間: 2011-5-17 12:50 AM