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The Maths Thread! |
maddav
Joined: Dec 01, 2002
Posts: 356
From: Nottingham, UK
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That's it, i remembered something!
it's about rotating across the x axis on 2 hyperbola, but I can't remember, i know you eventually you get the infinite surface area, and finite volume.
I remembered our physics teacher that was going on about theories of the 'shape' of the universe, and he expained the gabriel's horn shape, and we were asking if that was A-level, he said no, and that it was just kind of interesting..
well he was right 
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[ This Message was edited by: maddav on 2004-10-21 22:08 ] |
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kimcheeboi
Joined: Dec 19, 2003
Posts: > 500
From: Abducted by hot blondes to Les
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Sure, post your own problems! I'll post some linear algebra and differential eqs too if anyone wants. Btw to win the #1 you need to use 2 integrals. Very simple problem. ;-)
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mixin
Joined: Jan 26, 2002
Posts: > 500
From: Notts, UK
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I passed my A-level Maths 2 and a half years ago. Now managed to wipe all of it from the brain 
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RichLok
Joined: Jun 06, 2002
Posts: 331
From: Los Angeles, CA
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This is as far as I got in math... and that's by watching an episode of "The Simpsons". The one with Barney (The purple dinosaur) on it...
"Two plus two is four.... Two plus two is four... Two plus two is four...:"
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kimcheeboi
Joined: Dec 19, 2003
Posts: > 500
From: Abducted by hot blondes to Les
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here's a good one! 
A series circuit contains a resistor with R= 40 ohms, an inductor with L=2H, a capacitor with C=0.0025 F, and a 12-V batter. The initial charge is Q=.01C and the initial current is 0. Find the charge at time t. 
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maddav
Joined: Dec 01, 2002
Posts: 356
From: Nottingham, UK
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This is an easy one I did a couple of weeks ago, so it should be REALLY EASY for you lot!
Solve the equation to find the co-ordinates of each intersection
x(x-3) = x^2(1-x)
@Kimcheeboi: Damn, I can't do it, you seem to be posting all questions just out of my grasp, haven't covered inductors etc. in physics yet! 
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[ This Message was edited by: maddav on 2004-10-21 23:43 ] |
kimcheeboi
Joined: Dec 19, 2003
Posts: > 500
From: Abducted by hot blondes to Les
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x=plus or minus sqrrt or 3 or 0 
@maddav
fine!  
here ya go:
integrate:
x^3/(4x^2+9)^(3/2)
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maddav
Joined: Dec 01, 2002
Posts: 356
From: Nottingham, UK
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almost there Kim, but i said co-ordinates
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kimcheeboi
Joined: Dec 19, 2003
Posts: > 500
From: Abducted by hot blondes to Les
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i wasn't paying attention 
btw how are you supposed to find the coordinates of a linear equation? it's not even on a plane! 
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"conspiraqcy theories"-meths
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[ This Message was edited by: kimcheeboi on 2004-10-22 00:08 ] |
maddav
Joined: Dec 01, 2002
Posts: 356
From: Nottingham, UK
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OK, I'm really tired and I missed out the VERY top part of my notes (the y's), but i think this is what i did (that's re-assuring )
y=x(x-3)
y=x^2(1-x)
you should end up with what you got
(x)(x^2-3)
therefore y= (x)(x^2-3)
when x =0, y = 0
when x = +rt3
y= (rt3)(3-3)
y= 3-3rt3 or 3(1-rt3)
and the same for -rt3, i would do it, but I've got to go to bed now.
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[ This Message was edited by: maddav on 2004-10-22 00:34 ] |
maddav
Joined: Dec 01, 2002
Posts: 356
From: Nottingham, UK
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@anyone:
I've got some homework, and i solved this question, but the book says I'm wrong our teacher said there was a number of mistakes in it as well, so it's really annoying. Anyway, here it is, just the y values please, haven't bothered solving the x values yet.
Simultaneous equations:
x=2y-2
x^2 = y^2 +7
Thanks!
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[ This Message was edited by: maddav on 2004-10-28 18:22 ] |
50Cent
Joined: Nov 08, 2003
Posts: > 500
From: ...whatever psycho!!!
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x=2
y^2= -3
if u want explanation ask (check my answers with the books and urs)
Explanation:
take
x=2y-2 and square it
x^2=4y^2-2
x^2=y^2+7
rearrange
x^2 - 4y^2=-2
x^2 - y^2=7
subtract
-3y^2=9
divide by -3
y^2=-3
substitue into x^2=y^2+7
x^2= -3 +7
x^2=4
x=2
i'm probably wrong as always but its my offering 
50
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[ This Message was edited by: 50Cent on 2004-10-28 18:08 ]
[ This Message was edited by: 50Cent on 2004-10-28 18:15 ] |
BobaFett
Joined: Jan 06, 2004
Posts: > 500
From: Kamino (wish it would be Lund)
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When i was in general school, it was a usually question of math teachers to students: a ship is 55 m long and there are 273 passangers on board. How old is the captain?
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50Cent
Joined: Nov 08, 2003
Posts: > 500
From: ...whatever psycho!!!
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thats a tough one just gimme a month to find a 55m boat that has a 279 passenger capacity  den i'll just ask the captain
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maddav
Joined: Dec 01, 2002
Posts: 356
From: Nottingham, UK
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@boba:
@50: Ummm, it's a simultaneous equation, with an x^2 and y^2 values, so there should be 2 values for x. This is what i got:
x = 2y-2
x^2 = y^2 + 7
Substitute the value for x, into the second equation:
(2y-2)(2y-2) = y^2 + 7
= 4y^2 -4y -4y +4 = y^2 +7
= 3y^2 - 8y -11 = 0
= (y+1)(3y-11) = 0
y+1=0 y=-1
OR
3y-11=0 y=11/3
3y=11
y=11/3
That's the y values but the book has y=3 or -1/3
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Posted: 2004-10-21 22:57
ink p800:: 
urple t630:: 
