|
Author |
Message |
Erica
Joined: 11 Aug 2004Posts: 9
|
Posted: Fri Jan 21, 2005 7:48 pm Post subject: ╛Maths Q
|
|
|
1. 在三角形ABC中,已知A=60度,b=1,三角形ABC面積=根號3, 求(a+b+c)/(sinA+sinB+sinC) 2. 在三角形ABC中,a=m(m屬於正實數), b=6, A=30度, 要使c分別有一解,
兩解,無解,相應的m應滿足甚麼條件?
|
|
|
|
|
Wilson
Frequent VisitorJoined: 20 Oct 2004Posts: 74
|
Posted: Fri Jan 21, 2005 11:18 pm Post subject: Re: ╛Maths Q
|
|
|
1. 三角形面積
Cosine rule:
Sine rule: ,
(但我覺得會有更快的方法。)
2.
Discriminant =
c 有一解:
c 有兩解: or
c 為無解: |
|
|
|
|
Andy
Frequent VisitorJoined: 28 Oct 2003Posts: 391
Location: Hong Kong
|
Posted: Fri Jan 21, 2005 11:47 pm Post subject:
|
|
|
As , we have . The values of a and sin A are deduced as what Wilson did._________________
Patience and tolerance are necessarily demanded Year-round.
|
|
|
|
|
cs55555
Joined: 23 Aug 2004Posts: 19
|
Posted: Sat Feb 05, 2005 8:46 pm Post subject:
|
|
|
Andy wrote:
|
As , we have .
The values of a and sin A are deduced as what Wilson did.
|
我唔明點解會咁
|
|
|
|
|
142857
Joined: 01 Sep 2004Posts: 13
|
Posted: Sat Feb 05, 2005 9:46 pm Post subject:
|
|
|
Let a/sinA=b/sinB=c/sinC=k then a=ksinA, b=ksinB, c=ksinC (a+b+c)/(sinA+sinB+sinC) =k(sinA+sinB+sinC)/(sinA+sinB+sinC) =k
=a/sinA
|
|
|
|
|
|
|
|
All times are GMT + 8 Hours
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
|
|