A. Maths. Trigonometry Question

細薯

Originally posted by oscar at 2005-1-7 09:42 PM:

其實以前中三已經教左log，不過而家既syllabus改曬，越改越易...

=.=我只係對Maths、Physics同Chem係咁，其他科唔會咁熱愛...

yes~my Math. teacher always says that~~
chem is not teaching acid......not so difficult up till now

oscar

Originally posted by 落雷 at 2005-1-7 21:41:
今日份a.maths卷出現相似題目…好彩響試場好快就諗到了- -"

LHS=(1-cscA+cotA)/(1+cscA-cotA)

(1-cscA+cotA)(1+cscA)
=1-cscA+cotA+cscA-cscAcscA+cscAcotA
=1-cscAcscA-cscA+cscA+cotA+cscAcotA
...

下...你咁都得？
有d老屈成分wor...

抹茶可樂

Originally posted by oscar at 2005-1-7 09:44 PM:


下...你咁都得？
有d老屈成分wor...

真架…個個做到的人都係用「交叉相乘」

又例如Prove sin(A+B)=cos(A+B)
書會教你先Prove tan(A+B)=1

oscar

Originally posted by 落雷 at 2005-1-7 21:49:

真架…個個做到的人都係用「交叉相乘」

又例如Prove sin(A+B)=cos(A+B)
書會教你先Prove tan(A+B)=1

不過都有道理，但係好難諗到呢步...

水龍蜥

Originally posted by oscar at 2005-1-7 09:52 PM:


不過都有道理，但係好難諗到呢步...

你題數有冇人答你?

oscar

Originally posted by 水龍蜥 at 2005-1-8 16:09:

你題數有冇人答你?

落雷咪答左我lor...

oscar

Originally posted by 落雷 at 2005-1-7 21:41:
今日份a.maths卷出現相似題目…好彩響試場好快就諗到了- -"

LHS=(1-cscA+cotA)/(1+cscA-cotA)

(1-cscA+cotA)(1+cscA)
=1-cscA+cotA+cscA-cscAcscA+cscAcotA
=1-cscAcscA-cscA+cscA+cotA+cscAcotA
...

等等...我check到有好多錯處...
sec(90-A)=-cscA....
跟住(1-cscA+cotA)(1+cscA)在後面漏左個-cotA...

抹茶可樂

Originally posted by oscar at 2005-1-9 05:54 PM:

等等...我check到有好多錯處...
sec(90-A)=-cscA....
跟住(1-cscA+cotA)(1+cscA)在後面漏左個-cotA...

無問題呀