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# OCR C4 (not mei) 18th June 2013 revision watch

1. Does anyone have the jan 2013 paper? Please?
2. (Original post by strikerextreme)
which papers have you done besides ocr ? and are there any tricky questions worth looking at ? thx
i did an additional 6 specimen papers which were considerably easier than the actual exam papers themselves. The one i found most challenging out of the ones i did was jan 13 and an 11 paper as i made a couple of mistakes on some tricky questions.
3. (Original post by a10)
i did an additional 6 specimen papers which were considerably easier than the actual exam papers themselves. The one i found most challenging out of the ones i did was jan 13 and an 11 paper as i made a couple of mistakes on some tricky questions.
Oh **** jan 2013 is the one paper I haven't done as I have been unable to find a copy online.... Do you have one please?
4. (Original post by ihatepeople37)
Oh **** jan 2013 is the one paper I haven't done as I have been unable to find a copy online.... Do you have one please?
there i thought the DE was tricky...
Attached Images
5. 4724-01Jan13.pdf (201.5 KB, 87 views)
6. Just did Jan 2013 and got what I needed in it which is great. I am surprised the boundaries were so high (60/72 for 80 UMS) considering I thought a few of the questions were quite nasty. However most of the nasty questions were worth on a couple marks, and the last question on the paper was quite simple.

I didn't get the shape one on the vectors question on that paper though, apparently the correct answer was the least common answer!
7. (Original post by ihatepeople37)
So how do you prove intersection please?
they usually give you two line equations in form r=a+tb and r=a+sb where a isn't normally the same.
anyway.
say:
a+tb=a+sb for (i,j,k) values and then solve one( eg:i) to make t=x+5s say, then put it into the j equation. you can find one of the letters from that. Then go back to your equation you worked out t=x+5s to find t.
put your s and t into equation k.
If htey intersect, they will be equal. If not, they skew.

Hope that made some sense..
8. (Original post by a10)
find distance between A and B? how do u do that? or did u mean unit vectors?
you got two coordinates, A and B. do coordinate b-a = new coordinate.
i^2+j^2+k^2 then root that.
I think you can also call this " magnitude of line AB"
9. (Original post by joostan)
Ahh - ok.
If you like that kind've thing perhaps try:
You cycle it by parts until you get the original integral as one of the parts right? then you can simplify then solve

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10. (Original post by Genesis2703)
Just did Jan 2013 and got what I needed in it which is great. I am surprised the boundaries were so high (60/72 for 80 UMS) considering I thought a few of the questions were quite nasty. However most of the nasty questions were worth on a couple marks, and the last question on the paper was quite simple.

I didn't get the shape one on the vectors question on that paper though, apparently the correct answer was the least common answer!
i didn't like that shape one i hope we don't get anything like that tomoro also that second part of the DE was very tricky so many clues hidden in the paragraph...
11. (Original post by tinkerbell_xxx)
haha I've revised now
you'd be stupid not to have... D: what do you need??
12. (Original post by igloo1)
I really hope their's not too much weird vector stuff. Or horrible integration.
there's so much integration D: it counts as 3 separate topics, I think... Not good, don't like integration. But vectors are okay, I do mechanics as well so I'm not too bad with them :')
13. can anyone explain the jan 12 question 7 on vectors please! I just dont understand this stuff at all i can do the easy vector questions such as showing that they intersect or that they are skew etc but cant do these! please help mee!
14. (Original post by _theChief_)
there's so much integration D: it counts as 3 separate topics, I think... Not good, don't like integration. But vectors are okay, I do mechanics as well so I'm not too bad with them :')
Could you help me with something vectors related then? Or anyone else!

There are some questions which make you find out the point of intersection of 2 lines. That is easy. But then it says "There are two points on this line whose distance from the point of intersection is 10. FInd the position vector of one of these points." Any ideas?
15. (Original post by Morrison131)
can anyone explain the jan 12 question 7 on vectors please! I just dont understand this stuff at all i can do the easy vector questions such as showing that they intersect or that they are skew etc but cant do these! please help mee!
Yeah I am stuck on this one too.
16. (Original post by _theChief_)
there's so much integration D: it counts as 3 separate topics, I think... Not good, don't like integration. But vectors are okay, I do mechanics as well so I'm not too bad with them :')
same here. what really gets me is when you integrate a fraction, put the bottom on top to power -1 then have to to integrate it to make 0..
17. (Original post by Morrison131)
can anyone explain the jan 12 question 7 on vectors please! I just dont understand this stuff at all i can do the easy vector questions such as showing that they intersect or that they are skew etc but cant do these! please help mee!
Firstly the point p is on the line, which means it can be expressed in terms of the t variable. And if op is perpendicular to l it means its dot product with the direction vector of l will be 0. So you do the dot product and equate it to o and then solve for t, then substitute it in to the point p in terms of t to get p

Remember the vector op just means the point p

For the second part, again it's q in terms of t since q is on the line, then you do the standard formula for finding length of a vector on the point q since again oq is just the vector q. Then you have an equation in t to solve and since it involves squares you'll get a quadratic, meaning two solutions for t and this two points for q..
18. (Original post by joostan)
Ahh - ok.
If you like that kind've thing perhaps try:
Thanks, that was a nice one.

Spoiler:
Show
19. (Original post by a10)
i didn't like that shape one i hope we don't get anything like that tomoro also that second part of the DE was very tricky so many clues hidden in the paragraph...
Yeah but you just have to read the clues carefully and get your +/- signs right

One thing confuses me though, two lines are skew when A) they aren't parallel and B) they don't intesect, however on most questions saying "prove they are skew" you don't have to make any reference to condition A you just have to show they don't intersect. But occasionally you do have to mention that they aren't parallel. I find this really weird.

If you mention about the two lines not being parallel would you lose marks even if on most of the mark schemes this factor is not mentioned?
20. If you write -ln(0.5) instead of ln2 like it is in the mark scheme would you still get the marks? I always forget to change it!
21. (Original post by a10)
there i thought the DE was tricky...
do you have the mark scheme?

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