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CCEA A2 Maths C4 1st June 2012

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Reply 40
Original post by MatthewGallagher
i got them too except for the vectors one. i found the co-ordinates of P to be (-2,1,0)
I didn't know how to approach this question but i knew since that they were perpendicular, their dot product equalled zero. So i made a =(ai +bj +ck) and b = (-i-2j). Basically just used basic logic to get my answer. Really devastated with the Vol. of revolution, didn't have time to go back and check aswell because it took me three attempts on the proof. Anyone doing math at uni next year?


i'm really sorry to tell you this, but your co-ordinates for p don't fit on the line, as they don't substitute into the line equation.
Reply 41
Original post by star_5
I got the same co-ordinates (0,0,3) for P, but I used lamda, and got (2-lamda)i +(4-2lamda)j +3k, then worked that out as lamda =2. Are we on the same wave length here? lols


Yeah :smile: It's probably because there are multiple different equations you could have had for the line. I had r= i + 2j + 3k + t(-i - 2j) so you must of had something like r= 2i + 4j + 3k + lambda(-i - 2j) ?
Reply 42
Original post by sAuhsoj
why 92% specifically?


i need 92% cos i want an a* seeing as i doing maths at queens nect year, so i need 180 marks between c3 and c4, and i only got 88 in c4, hence i need 92 in this
Reply 43
Original post by star_5
Got the same as you for the paperweight thing! 512pi over something lol


Sorry, think you may have got that wrong (hope so, otherwise I did :P).
You had to find the volume when rotated 360 degrees between x-axis, the curve AND THE Y-AXIS (ie x = 0).

Integrating between 2 and -2 gives you 512/15 pi

Integrating between 2 and 0 gives you 256/15 pi
Reply 44
Original post by Guin

I got 512 pi over something..I've forgotten the bottom line of the fraction :frown:

for the love of all that is holy, please tell me that was 512pi over 15!
can someone who got q6. the vectors question fully right be able to upload their solution to i deduce how many follow through marks i might achieve, thanks!
Reply 46
Original post by MatthewGallagher
can someone who got q6. the vectors question fully right be able to upload their solution to i deduce how many follow through marks i might achieve, thanks!


I have written it all out for you at http://goo.gl/aZl4P
Reply 47
now I really must get back to revision
Reply 48
Original post by wormyrug
for the love of all that is holy, please tell me that was 512pi over 15!


sorry mate, pretty sure it was 256/15 pi
Reply 49
Original post by sAuhsoj
sorry mate, pretty sure it was 256/15 pi


oh, perhaps i made a mistake with the limits, i used 2 and -2, although as i type this, i realise the question said between the y-axis, so should be 2 and 0
Reply 50
How many marks do you reckon will be lost for using the bottom limit as -2 instead of 0?
Original post by sAuhsoj
I have written it all out for you at http://goo.gl/aZl4P


thanks bro, i messed up part ii). i just used the direction vector of the line l as the position vector OP. oh well, apart from that and the vol of revolution mishap it all went swell :smile:
where are you for next year?
Reply 52
Original post by MatthewGallagher
thanks bro, i messed up part ii). i just used the direction vector of the line l as the position vector OP. oh well, apart from that and the vol of revolution mishap it all went swell :smile:
where are you for next year?


Still in school (unfortunately), doing further maths so sat the exam with the Year 14s. You?
Reply 53
Original post by star_5
How many marks do you reckon will be lost for using the bottom limit as -2 instead of 0?


one and no more; you had the right method and knew the formula - can't penalise you any more
Reply 54
Original post by sAuhsoj
one and no more; you had the right method and knew the formula - can't penalise you any more


Haha in our correspondence you have simultaneously panicked me and set my mind at ease :L
Reply 55
Original post by star_5
Haha in our correspondence you have simultaneously panicked me and set my mind at ease :L


well it is good they came that way round :smile:
Reply 56
Original post by sAuhsoj
one and no more; you had the right method and knew the formula - can't penalise you any more


Yay! Only mark I've lost :smile:
Reply 57
Original post by Guin
Yay! Only mark I've lost :smile:

Haha wish I had your confidence!
Reply 58
Original post by star_5
Haha wish I had your confidence!


How did you find the rest of the paper? I had given my maths teacher my answers for the questions and he did he paper and checked mine. The only answer of mine he wasn't sure of was the volume of revolution because he said the question wasn't clear. :P
Reply 59
Original post by Guin
How did you find the rest of the paper? I had given my maths teacher my answers for the questions and he did he paper and checked mine. The only answer of mine he wasn't sure of was the volume of revolution because he said the question wasn't clear. :P


Tbh I think I'm the same as you, ie the only one I know for sure I did wrong is the volume of revolution one due to the wrong lower limit! But I keep worrying haha eg in the one mark part of the vectors question, I'm not sure if I wrote it right? At the end of the day I probably did? But I worry nonetheless haha

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