Current Year 12 Thread Mark I (2012-2013) Watch

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justinawe
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#7521
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#7521
(Original post by Abject Testament)
Same
Did you do IGCSEs as well?
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Abject Testament
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#7522
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#7522
Mixture of IGCSEs and normal gcses
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L'Evil Fish
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#7523
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#7523
Just in awe, can you check this, volume of revolution, of y = x + 3/Rootx between 1 and 4.

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y = x + 3/Rootx between 1 and 4.

Pi *integral* y^2 dx
Pi *integral* (x^2 + 6x/Rootx + 9/x) dx
Pi *integral* (x^2 + 6x(x^-1/2) + 9(x^-1)) dx

Pi *intergral* x^2 + *integral* 6x^(1/2) + *integral* 9/x

Pi [x^3/3 + 4x^(3/2) + 9ln|x|]

Excuse lack of latex...


Is that right so far?

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justinawe
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#7524
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#7524
(Original post by L'Evil Fish)
Just in awe, can you check this, volume of revolution, of y = x + 3/Rootx between 1 and 4.

y = x + 3/Rootx between 1 and 4.

Pi *integral* y^2 dx
Pi *integral* (x^2 + 6x/Rootx + 9/x) dx
Pi *integral* (x^2 + 6x(x^-1/2) + 9(x^-1)) dx
Pi [x^3/3 + 3/Rootx -9/x^2]
Pi [(64/3 + 3/2 - 9/16)-(1/3 + 3 - 9)]
Pi (1053/48+ 272/48)
Pi (1325/48)
1325Pi/48

Excuse lack of latex...


Is that right so far?

My Username is really Poisson Distribution :mmm:
Not quite sure how you got this... think you integrated it wrong.
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L'Evil Fish
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#7525
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#7525
(Original post by justinawe)
Not quite sure how you got this... think you integrated it wrong.
:facepalm:

I differentiated the second bits randomly xD

Re check the edit?

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justinawe
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#7526
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#7526
(Original post by L'Evil Fish)
:facepalm:

I differentiated the second bits randomly xF

My Username is really Poisson Distribution :mmm:
:rofl:

Think it should be \pi \left[ \frac{x^3}{3} + 4x^{\frac{3}{2}} + 9\ln x \right]_1^4
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L'Evil Fish
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#7527
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#7527
(Original post by justinawe)
:rofl:

Think it should be \pi \left[ \frac{x^3}{3} + 4x^{\frac{3}{2}} + 9\ln x \right]_1^4
Yeah I have that now! (in the edit)

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justinawe
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#7528
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#7528
(Original post by L'Evil Fish)
Yeah I have that now! (in the edit)

My Username is really Poisson Distribution :mmm:
Good reading that was a massive pain... I read it wrong at first and got a completely different answer! Learn LaTeX please
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L'Evil Fish
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#7529
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#7529
(Original post by justinawe)
Good reading that was a massive pain... I read it wrong at first and got a completely different answer! Learn LaTeX please
:rofl: sorry
Okay, how do I latex fractions...

Do I have to type in, frac?
And how about Integral sign? And limits?

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L'Evil Fish
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#7530
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#7530
Spoiler:
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 /int [(3x+1)(e^2x)] dx


Oh I give up with latex...

(3x+1) + (1/2)e^2x - *integrate* (1/2)e^2x + 3 dx

Numbers in wrong?

Lol, made that up, did that come up in latex!?

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Deziah
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#7531
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#7531
All I can see is maths I don't understand. :eek:
What module is all this?
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usycool1
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#7532
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#7532
(Original post by Deziah)
All I can see is maths I don't understand. :eek:
What module is all this?
Volumes of revolution is C4 if you're with Edexcel (not sure about other exam boards though).
L'Evil Fish
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#7533
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#7533
(Original post by usycool1)
Volumes of revolution is C4 if you're with Edexcel (not sure about other exam boards though).
I need Latex tutorials lol, it's C4 with me as well

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Zeionic
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#7534
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#7534
(Original post by Deziah)
All I can see is maths I don't understand. :eek:
What module is all this?
No idea, I believe it's C4 ( From what Usycool said )....This looks hard...

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Where did you get Pi from y = x + 3/Rootx between 1 and 4. :O
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L'Evil Fish
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#7535
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#7535
(Original post by Sheel1)
No idea, I believe it's C4 ( From what Usycool said )....This looks hard...
When you learn it, it'll be fine

Integration (simple start, is opposite of differentiation) so you add one to the power and divide the co efficient by it.

If you differentiate 3x^2 + 4x + 1 you'd get 6x + 4.

If you integrate 6x + 4. You'd get 3x^2 + 4x + c (because c could be any number, we don't know it's 1)

Think of it as anti differentiation, and you can use it to find area under a graph, volume of 3D shapes

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L'Evil Fish
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#7536
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#7536
(Original post by Sheel1)
No idea, I believe it's C4 ( From what Usycool said )....This looks hard...

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Where did you get Pi from y = x + 3/Rootx between 1 and 4. :O
It's a rule
To find the volume generated by a graph being rotated 360 degrees. You integrate the graph squared and multiply it by Pi

Eg y = x spin it around 360 degrees, what's the.volume between 1 and 2.

square y and you get x^2 right? So integrate that and do things (you'll learn soon) and multiply by pi!

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usycool1
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#7537
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#7537
(Original post by Sheel1)
No idea, I believe it's C4 ( From what Usycool said )....This looks hard...

Spoiler:
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Where did you get Pi from y = x + 3/Rootx between 1 and 4. :O
Have you done C2 yet? If not, it'll be hard to explain where the pi comes from.

(Original post by L'Evil Fish)
I need Latex tutorials lol, it's C4 with me as well

My Username is really Poisson Distribution :mmm:
This is quite useful: http://www.thestudentroom.co.uk/wiki/LaTex
justinawe
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#7538
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#7538
(Original post by L'Evil Fish)
Spoiler:
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 /int [(3x+1)(e^2x)] dx


Oh I give up with latex...

(3x+1) + (1/2)e^2x - *integrate* (1/2)e^2x + 3 dx

Numbers in wrong?

Lol, made that up, did that come up in latex!?

My Username is really Poisson Distribution :mmm:
Close :rofl: it's \int, not /int

Just read the article http://www.thestudentroom.co.uk/wiki/LaTex

When I was first learning how to use it, I kept referring to the article on how to do stuff. Now it just comes naturally
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L'Evil Fish
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#7539
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#7539
(Original post by justinawe)
Close :rofl: it's \int, not /int

Just read the article http://www.thestudentroom.co.uk/wiki/LaTex

When I was first learning how to use it, I kept referring to the article on how to do stuff. Now it just comes naturally
Just read it :lol: were the answers right? For integration by parts?

\int(3x+1)(e^{2x})dx
(3x+1)[(e^{2x})/2]-\int[\frac{e^{2x}}{2} + 3] dx

[\frac{(3x)(e^{2x}) + e^{2x}}{2}] - \frac{e^{2x}}{4} + 3x

:lol:

:lol: trying my new skillz
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justinawe
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#7540
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#7540
(Original post by L'Evil Fish)
Just read it :lol: were the answers right? For integration by parts?

\int(3x+1)(e^{2x})dx

My Username is really Poisson Distribution :mmm:
I don't see no answers
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