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25 May 2003, 20:54
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#1
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Stoke
Join Date: Apr 2000
Posts: 92
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a maths question...
find dy/dx of ln(1+tan^2 x)
How does one go about solving this?
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25 May 2003, 21:01
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#2
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Lord Denning
Join Date: Feb 2003
Location: City of London
Posts: 2,548
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Differential of ln(something) is ( 1/(something) x (differential of something)) I think.
I can't remember what the differential of tan^2 is though. tan^2 sec^2 sounds familiar however.
If it is (and don't take my word for it), the answer would be ((tan^2 x)(sec^2 x)) / (1 + (tan^2 x)).
However, (1 + tan^2 x) is (sec^2 x) I think, which would make the whole thing (tan^2 x).
Don't believe me though, I'm a Classicist!
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Please bear in mind when reading the above post that I am always right.
Quote:
Originally Posted by Marilyn Manson
He was crowned in York Cathedral as 'Expert in the West' by Pope Urban III in 1186.
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25 May 2003, 21:03
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#3
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NEWSBOT
Join Date: Dec 2000
Location: The enby cave!
Posts: 4,872
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paging Mrl_Jakiri to thread 164612
paging Sarina_Joy to thread 164612
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[20:27:47] <nodrog-aawy> **** i think my housemate just caught me masturbating
[11:25:32] <idimmu> you are a little piggy arent you
[13:17:00] <KaneED> i'm so closet i'm like narnia
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Pretty parks and funky scrap metal things here
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25 May 2003, 21:04
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#4
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The Twilight of the Gods
Join Date: Jan 2001
Posts: 23,481
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Very easily.
Proteus is right you know. (1/something) * d (something) / dx.
Ps. 1 + tan^2 = sec^2.
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25 May 2003, 21:05
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#5
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Lord Denning
Join Date: Feb 2003
Location: City of London
Posts: 2,548
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Quote:
Originally posted by MrL_JaKiri
Very easily.
Proteus is right you know. (1/something) * d (something) / dx.
Ps. 1 + tan^2 = sec^2.
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I am? That's amazing! I thought I'd forgotten Maths.
__________________
Please bear in mind when reading the above post that I am always right.
Quote:
Originally Posted by Marilyn Manson
He was crowned in York Cathedral as 'Expert in the West' by Pope Urban III in 1186.
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25 May 2003, 21:05
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#6
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Gubbish
Join Date: Sep 2000
Location: #FoW
Posts: 2,323
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Re: a maths question...
Quote:
Originally posted by '|'empest
find dy/dx of ln(1+tan^2 x)
How does one go about solving this?
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First of all, I am unsure on the notation tan^2 x, but will assume it means (tan(x))^2 (which I write as tan(x)^2, call me a coder)
also, I write dy/dx of f(x) as f(x)'
ln(u(x))'=u'(x)/u(x)
u(x)=1+tan(x)^2=sec(x)^2
u'(x)=2tan(x)*sec(x)^2
ln(1+tan(x)^2)'=2tan(x)sec(x)^2/sec(x)^2=2tan(x)
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Gubble gubble gubble gubble
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25 May 2003, 21:13
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#7
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Stoke
Join Date: Apr 2000
Posts: 92
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Danke.
I knew it was a composite function, and that it would be 1/x * dy/dx of tan^2 x, but didn't have an effing clue what that was.
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25 May 2003, 21:37
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#8
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Kontrč*******
Join Date: Apr 2003
Location: where ever you want me hun
Posts: 168
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int(ln(1+tan(x)^2)*dx)
Help me on this one please
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25 May 2003, 21:42
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#9
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Gubbish
Join Date: Sep 2000
Location: #FoW
Posts: 2,323
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Quote:
Originally posted by Anu
int(ln(1+tan(x)^2)*dx)
Help me on this one please
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No?
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Gubble gubble gubble gubble
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25 May 2003, 21:42
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#10
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Kontrč*******
Join Date: Apr 2003
Location: where ever you want me hun
Posts: 168
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please, pretty please!
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25 May 2003, 21:46
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#11
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Registered User
Join Date: Jun 2000
Posts: 8,476
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Quote:
Originally posted by Anu
int(ln(1+tan(x)^2)*dx)
Help me on this one please
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I solved it in a truly remarkable way, but unfortunately this post is too small to contain the solution.
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25 May 2003, 21:48
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#12
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Kontrč*******
Join Date: Apr 2003
Location: where ever you want me hun
Posts: 168
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Quote:
Originally posted by Nodrog
I solved it in a truly remarkable way, but unfortunately this post is too small to contain the solution.
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Maple is ghey
meaple too?
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25 May 2003, 21:50
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#13
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Lord Denning
Join Date: Feb 2003
Location: City of London
Posts: 2,548
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Quote:
Originally posted by Anu
Maple is ghey
meaple too?
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Eh?
__________________
Please bear in mind when reading the above post that I am always right.
Quote:
Originally Posted by Marilyn Manson
He was crowned in York Cathedral as 'Expert in the West' by Pope Urban III in 1186.
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25 May 2003, 21:51
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#14
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Registered User
Join Date: Oct 2000
Posts: 4,944
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Quote:
Originally posted by Anu
int(ln(1+tan(x)^2)*dx)
Help me on this one please
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do what W did in reverse
int (f(x)'/f(x)) = ln(f(x))
etc
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25 May 2003, 21:54
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#15
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The Twilight of the Gods
Join Date: Jan 2001
Posts: 23,481
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Quote:
Originally posted by Ragnarak
do what W did in reverse
int (f(x)'/f(x)) = ln(f(x))
etc
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You could do that if it was the derivative of a function divided by the function, but unfortunately it isn't.
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25 May 2003, 21:54
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#16
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The Twilight of the Gods
Join Date: Jan 2001
Posts: 23,481
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ps it's f'(x), at least in England and America.
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25 May 2003, 21:56
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#17
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Registered User
Join Date: Oct 2000
Posts: 4,944
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Quote:
Originally posted by MrL_JaKiri
You could do that if it was the derivative of a function divided by the function, but unfortunately it isn't.
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oops (i only half read it )
and erm oops again
nm
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I find it kind of funny
I find it kind of sad
The dreams in which i'm dying
Are the best i've ever had
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25 May 2003, 23:22
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#18
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Registered User
Join Date: Oct 2001
Posts: 940
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Thankyou for reminding me why I quit maths a few weeks ago I was almost regretting it
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25 May 2003, 23:35
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#19
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The Twilight of the Gods
Join Date: Jan 2001
Posts: 23,481
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What, applying a really really simple rule?
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25 May 2003, 23:41
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#20
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Kontrč*******
Join Date: Apr 2003
Location: where ever you want me hun
Posts: 168
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maths is following rules
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25 May 2003, 23:41
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#21
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Lord Denning
Join Date: Feb 2003
Location: City of London
Posts: 2,548
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Maths is fun.
__________________
Please bear in mind when reading the above post that I am always right.
Quote:
Originally Posted by Marilyn Manson
He was crowned in York Cathedral as 'Expert in the West' by Pope Urban III in 1186.
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25 May 2003, 23:45
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#22
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Banned
Join Date: Dec 2000
Location: autogenic misery
Posts: 872
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Quote:
Originally posted by MrL_JaKiri
ps it's f'(x), at least in England and America.
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the dy/dx style notation is also used.
f'(x), f''(x) etc. is the french notation.
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25 May 2003, 23:45
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#23
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Gubbish
Join Date: Sep 2000
Location: #FoW
Posts: 2,323
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It's a whole 'nother ball of wax, and one of the reasons I tired of maths.
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Gubble gubble gubble gubble
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25 May 2003, 23:46
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#24
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The Twilight of the Gods
Join Date: Jan 2001
Posts: 23,481
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Quote:
Originally posted by inf
both are used, it's the french notation.
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That's no excuse!
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25 May 2003, 23:48
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#25
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Banned
Join Date: Dec 2000
Location: autogenic misery
Posts: 872
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Quote:
Originally posted by MrL_JaKiri
That's no excuse!
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I have only studied A-Level Maths, we use the dy/dx style.
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25 May 2003, 23:51
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#26
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Kontrč*******
Join Date: Apr 2003
Location: where ever you want me hun
Posts: 168
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Physicist tend to use the dot thing don't they?
(one dot above f(x) means the first derivative, two dots means the second, and so on)
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25 May 2003, 23:56
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#27
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The Twilight of the Gods
Join Date: Jan 2001
Posts: 23,481
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Quote:
Originally posted by Anu
Physicist tend to use the dot thing don't they?
(one dot above f(x) means the first derivative, two dots means the second, and so on)
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f dash x usually.
f double dash etc.
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26 May 2003, 00:04
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#28
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Kontrč*******
Join Date: Apr 2003
Location: where ever you want me hun
Posts: 168
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Method 4
right. used in dynamics and the like
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26 May 2003, 00:10
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#29
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The Twilight of the Gods
Join Date: Jan 2001
Posts: 23,481
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I know what it is, I've used it in mechanics at A-level, just never in physics.
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26 May 2003, 00:15
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#30
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Registered User
Join Date: Oct 2001
Posts: 940
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Quote:
Originally posted by MrL_JaKiri
What, applying a really really simple rule?
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Not at all, I could do it... Was just that its boring and pointless
(yes i know this doesn't apply to everyone)
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26 May 2003, 00:18
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#31
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The Twilight of the Gods
Join Date: Jan 2001
Posts: 23,481
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It being pointless is independent on the individual.
And it isn't.
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26 May 2003, 00:20
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#32
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Registered User
Join Date: Oct 2001
Posts: 940
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Quote:
Originally posted by MrL_JaKiri
It being pointless is independent on the individual.
And it isn't.
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No. Its pointless for me to do... Sorry for my phrasing.
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26 May 2003, 09:39
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#33
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Registered User
Join Date: Feb 2002
Location: South Pacific
Posts: 4,911
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you lot conjugate.
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I think it's time we blow this scene, get everybody and the stuff together..........
ok 3..... 2..... 1.. let's jam
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26 May 2003, 09:59
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#34
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Lord Denning
Join Date: Feb 2003
Location: City of London
Posts: 2,548
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Quote:
Originally posted by Radical Edward
you lot conjugate.
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No, that would be me.
__________________
Please bear in mind when reading the above post that I am always right.
Quote:
Originally Posted by Marilyn Manson
He was crowned in York Cathedral as 'Expert in the West' by Pope Urban III in 1186.
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26 May 2003, 11:06
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#35
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Hell
Join Date: Aug 2001
Location: England, Kent
Posts: 96
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i hate differentiating with ln
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26 May 2003, 11:09
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#36
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Registered User
Join Date: Feb 2002
Location: South Pacific
Posts: 4,911
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Quote:
Originally posted by Fleet_Multiplex
i hate differentiating with ln
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you especially.
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I think it's time we blow this scene, get everybody and the stuff together..........
ok 3..... 2..... 1.. let's jam
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26 May 2003, 16:22
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#37
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Banned
Join Date: Dec 2000
Location: autogenic misery
Posts: 872
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Quote:
Originally posted by Anu
Physicist tend to use the dot thing don't they?
(one dot above f(x) means the first derivative, two dots means the second, and so on)
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That's the newton style notation, rarely used.
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26 May 2003, 16:38
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#38
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mmm.. pills
Join Date: Apr 2000
Location: Australia
Posts: 2,152
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Ack!:eek:
Just gives me headaches looking at those formulas. Despite my efforts, I never did find any fun in maths. Especially since I loath to work with unknown variables.
=[DJ Bass]=
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CSS : the result of letting artists design something only an engineer should touch.
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26 May 2003, 20:20
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#39
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The Twilight of the Gods
Join Date: Jan 2001
Posts: 23,481
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Yeah, the presence of this + thing scares me too.
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27 May 2003, 07:50
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#40
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Registered User
Join Date: Feb 2002
Location: South Pacific
Posts: 4,911
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Quote:
Originally posted by inf
That's the newton style notation, rarely used.
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pretty much only used in position velocity and acceleration as far as I know.
Dirac notation > |*>
__________________
I think it's time we blow this scene, get everybody and the stuff together..........
ok 3..... 2..... 1.. let's jam
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29 May 2003, 12:09
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#41
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Ball
Join Date: Oct 2001
Posts: 4,410
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Quote:
Originally posted by Radical Edward
pretty much only used in position velocity and acceleration as far as I know.
Dirac notation > |*>
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more like |*⟩
I would like help with this question:
Given that y=x^sinh x, prove that
y d²y/dx² - (dy/dx)² = y²/x
My attempt follows:
take logarithms,
ln y = sinhx ln x
differentiate wrt x,
1/y dy/dx = 1/x sinh x + coshx ln x
differentiate wrt x,
1/y d²y/dx² - 1/y² (dy/dx)² = 1/x cosh x - 1/x² sinh x + 1/x coshx + sinh x ln x
multiply by y²,
y d²y/dx² - (dy/dx)² = y²/x ( 2 cosh x - 1/x sinh x + x sinh x ln x )
The question might be wrong but it's doubtful.
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30 May 2003, 02:36
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#42
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Ball
Join Date: Oct 2001
Posts: 4,410
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30 May 2003, 05:04
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#43
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The Twilight of the Gods
Join Date: Jan 2001
Posts: 23,481
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Give me a minute, need to find some paper.
[edit]
Can't find any paper.
Do it tomorrow.
Last edited by MrL_JaKiri; 30 May 2003 at 05:53.
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30 May 2003, 06:11
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#44
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Registered User
Join Date: Feb 2002
Location: South Pacific
Posts: 4,911
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Quote:
Originally posted by queball
more like |*⟩
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maybe your keyset is different. all I see instead of your > is a box. what do you see instead of mine?
__________________
I think it's time we blow this scene, get everybody and the stuff together..........
ok 3..... 2..... 1.. let's jam
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30 May 2003, 15:29
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#45
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Ball
Join Date: Oct 2001
Posts: 4,410
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Quote:
Originally posted by Radical Edward
maybe your keyset is different. all I see instead of your > is a box. what do you see instead of mine?
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The ket part of a Dirac vector thing, it look sjust like on http://mathworld.wolfram.com/DiracNotation.html
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30 May 2003, 15:48
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#46
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Kontrč*******
Join Date: Apr 2003
Location: where ever you want me hun
Posts: 168
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Did you try using sinh x = 1/2 (e^x - e^-x)
Prolly won't make any difference though.
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30 May 2003, 15:59
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#47
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Registered User
Join Date: Feb 2002
Location: South Pacific
Posts: 4,911
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ok, so either you were point in at my use of the greater than symbol > or saying that Dirac notation = |*>
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I think it's time we blow this scene, get everybody and the stuff together..........
ok 3..... 2..... 1.. let's jam
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30 May 2003, 16:07
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#48
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Cute and cuddly
Join Date: Jul 2002
Location: New York
Posts: 1,891
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omg nerd alert!^99
the answer is
2 4mathz
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