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# Edexcel C3,C4 June 2013 Thread watch

I get the coefficient of x^2 as 8/27 instead of 4/27 and x^3 as 40/243 instead of 40/729!
thank you

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Is your simplified expansion like this? The x3 coefficient is probably from the same initial error.

Excuse horrible drawings.
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2. (Original post by MasterYi)
dV/dh means it is with respect to h(height). So so it is the 'x' in the equation.

If it was dV/dr then 2πrh would be correct.

ahhhh your a life saver, yeah that makes sense thanks.

The question didn't actually say what to differentiate with respect to, but do you just choose which ever variable is changing? because the radius wasn't changing in the question
3. (Original post by Myocardium)
Yeah and all the other identities such as inegral of 1/ax+b = 1/a ln(ax+b)
I'm gonna make some notes on that after I revise for biology so I'll let you know
4. (Original post by physicso)
ahhhh your a life saver, yeah that makes sense thanks.

The question didn't actually say what to differentiate with respect to, but do you just choose which ever variable is changing? because the radius wasn't changing in the question
They don't usually tell yo, so you have to make up you own.

Yes I'm assuming thats right, the height is the variable so it can change.
5. (Original post by MasterYi)
Is your simplified expansion like this? The x3 coefficient is probably from the same initial error.

Excuse horrible drawings.
i completely forgot about the factorials when doing it so that was a stupid mistake by me! but thank you master yi
6. Can someone give a clear definition of induced fission

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7. (Original post by cooldudeman)
Can someone give a clear definition of induced fission

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With numbers or neutrons?
8. (Original post by MasterYi)
With numbers or neutrons?
Neutrons and atomic numbers

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9. (Original post by nukethemaly)
I'm gonna make some notes on that after I revise for biology so I'll let you know
Okay thanks

(Original post by cooldudeman)
Can someone give a clear definition of induced fission

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Do we need to know this for C4
10. (Original post by cooldudeman)
Neutrons and atomic numbers

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I was trying to say wrong thread.

Here's a physics thread which maybe able to help.
http://www.thestudentroom.co.uk/show....php?t=2244676
11. C4 solomon B question 8b jesus christ that took longer than any question I've done before, so much working out

Haven't seen a vectors one like that before (with squared lambda etc), the same method applies but half way through I was convinced I was doing it wrong as it was way more than what you usually have to do, finally got there though
Why was this paper so much easier? I swear I could have got an A on this one.
If the UMS system works properly, the difficulty of the paper shouldn't make any real difference to your final grade. Perhaps you have got an A.

So, hard as it is to follow, the best advice is to stop worrying about the fact that you were given a hard paper, and just carry on with your life. (C4, for example? )
13. I'm really stuck on q6a of C4 Solomon A. It's only a 4 marker so it shouldn't be too complicated, but I just DON'T UNDERSTAND AT ALL.

The question is to find the integral (don't know how to do the squiggle) of 2sin3xsin2x dx

14. Do we have to know the formulas for different areas and volumes such as cones and spheres off by heart? Or will the be given with the question if we need them?
15. (Original post by Minumi)
I'm really stuck on q6a of C4 Solomon A. It's only a 4 marker so it shouldn't be too complicated, but I just DON'T UNDERSTAND AT ALL.

The question is to find the integral (don't know how to do the squiggle) of 2sin3xsin2x dx

Use the identity cos(a) - cos(b) = -2sin(A+B/2)sin(A-B/2)

That's A+B all over 2 and A-B all over 2 btw.
16. (Original post by Knoyle quiah)
How to do the last part of this question??? can someone show me the diagram they get please, myne seems to be wrong or the mark scheme is wrong
someone help
17. (Original post by Minumi)
I'm really stuck on q6a of C4 Solomon A. It's only a 4 marker so it shouldn't be too complicated, but I just DON'T UNDERSTAND AT ALL.

The question is to find the integral (don't know how to do the squiggle) of 2sin3xsin2x dx

Do cos(3x-2x) - cos(3x-2x) ie. (cox3xcos2x + sin3xsin2x) - (cos3xcos2x - sin3xsin2x) and work it out from there. There are similar questions to this in one of the exercises in the C4 text book. I just did this paper the other day so happened to have my method close by.
18. Guys I have a problem with my calculator (a normal everyday casio fx-85gt plus). I managed to press a couple of buttons all at once and I don't know what I've done but it's now come up as having TRUE/FALSE at the bottom of the screen. How do I bring it back to normal (and what would I press to bring up this function again (that I never knew existed)).
19. (Original post by Knoyle quiah)
How to do the last part of this question??? can someone show me the diagram they get please, myne seems to be wrong or the mark scheme is wrong
Should be
20. c4 book page 46 question 10 help?? im so confused://

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