ltw

今年份 m2 深淺程度如何?

Mr.Somebody

比上2年容易

economic

客觀分析介乎2012和2013中間，5**curve 86-88%
呢份一定唔會淺過2012

ACOMG

Part A多左伏位的感覺tetrahedron要cross product除2再除3果下

Part B反而感覺淺左,多左show野果d
除左matrix乘到high high之外感覺還OK
(p.s.條integration真係好淺

)

andylong

引用:

原帖由 ACOMG 於 2014-4-29 12:51 PM 發表
Part A多左伏位的感覺tetrahedron要cross product除2再除3果下

Part B反而感覺淺左,多左show野果d
除左matrix乘到high high之外感覺還OK
(p.s.條integration真係好淺)

我第1條就錯在, 好唔小心
Part A integration 唔知點解計到負數
睇完你個tetrahedral就......:L
Part B第1題個1分題我用tan(theta)寫, 開方入面有5-6個term, 之後都冇心機做
Matrix又煩到喊, 慘過2012果個好多
份野唔難, 但真係好煩, 仲要好小心em16em16em16em16em16em16em16em16

gavccf

真心今年M2真係淺咗
BTW,有冇人SHARE下啲ANSWER

y_1013

Part B q1
我記得好似個長度係24sec(theta)+192csc(theta)

andylong

引用:

原帖由 y_1013 於 2014-4-29 01:40 PM 發表
Part B q1
我記得好似個長度係24sec(theta)+192csc(theta)

如果個長方形係24*192
我個方法係3個similar triangles
192/x=y/24=(y+192)/(x+24)=tan(theta)
y=4608/x
Pyth thm, root((192+y)^2+(24+x)^2)=root((192+4608/x)^2+(24+x)^2)
=root(37440+1769472/x+21233664/x^2+48x+x^2)
Since x=192/tan(theta)
=root(37440+1769472/x+21233664/x^2+48x+x^2)
=root(37440+9216tan(theta)+576(tan(theta))^2+9216cot(theta)+36864(cot(theta))^2)
歡迎各位指點錯處, 不過錯在會令我好過d, 因為呢個搞到我part b冇做

y_1013

點解你會有3個similar tri@@?

得2個咋bor    一個係個bookshelf 上面   一個係下面

佢地個個角係一樣架bor@@    個bookshelf  深24cm   高192 cm

maylie

淺左

andylong

引用:

原帖由 y_1013 於 2014-4-29 02:03 PM 發表
點解你會有3個similar tri@@?

得2個咋bor    一個係個bookshelf 上面   一個係下面

佢地個個角係一樣架bor@@    個bookshelf  深24cm   高192 cm

唔係一個係長方形上面, 一個係長方形右面, 一個係成個大三角形咩?

y_1013

唔知有冇記錯....
更正翻  sin(theta)=192/CK   唔係HK

[ 本帖最後由 y_1013 於 2014-4-29 02:13 PM 編輯 ]

andylong

引用:

原帖由 y_1013 於 2014-4-29 02:09 PM 發表
唔知有冇記錯....
更正翻  sin(theta)=192/CK   唔係HK

Yes I see I couldn't think about this at that time
But does my method get wrong?
Referring to your graph, HCD similar to CKB similar to HKA
HD/DC=CB/BK=HA/AK=tan(theta)
And finally I got something that I wrote on #8
(As well, I let HD=x and BK=y)

[ 本帖最後由 andylong 於 2014-4-29 02:27 PM 編輯 ]

y_1013

i think ur method is acceptable.
but u may spend more time to finish this question.

i dont remember how many scores in this question.

andylong

引用:

原帖由 y_1013 於 2014-4-29 02:30 PM 發表
i think ur method is acceptable.
but u may spend more time to finish this question.

i dont remember how many scores in this question.

1mark But 5marks in partB
It's impossible to solve the derivative = 0
Next year, EAA should ask " Prove that root(37440+9216tan(theta)+576(tan(theta))^2+9216cot(theta)+36864(cot(theta))^2) = 24sec(theta)+192csc(theta)"
EAA   !!!!!!!!