[wormyrug]

(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.

[Guin]

(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 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) ?

[wormyrug]

(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

[sAuhsoj]

(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

[wormyrug]

(Original post by Guin)
I got 512 pi over something..I've forgotten the bottom line of the fraction

for the love of all that is holy, please tell me that was 512pi over 15!

[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!

[sAuhsoj]

(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

[sAuhsoj]

now I really must get back to revision

[sAuhsoj]

(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

[wormyrug]

(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

[star_5]

How many marks do you reckon will be lost for using the bottom limit as -2 instead of 0?

[MatthewGallagher]

(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
where are you for next year?

[sAuhsoj]

(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
where are you for next year?

Still in school (unfortunately), doing further maths so sat the exam with the Year 14s. You?

[sAuhsoj]

(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

[star_5]

(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

[sAuhsoj]

(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

[Guin]

(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

[star_5]

(Original post by Guin)
Yay! Only mark I've lost

Haha wish I had your confidence!

[Guin]

(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

[star_5]

(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