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

1. (Original post by zmai)
Thankyou!! I forgot to plug x values back in to find y values for question 4.

Would it be okay to write 1/2ln(root3) ? Did they specify the format?

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I think that this would be okay because the question never specified what type of numbers "a" and "b" needed to be (i.e. rational, integer etc.) when in the form a ln(b).
2. Anyone have any idea of what grade boundaries will be?

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3. (Original post by a10)
but cos x cant be zero the limits of x where greater than zero and less than pi? therefore u can divide by cos?
EDIT: Cos(pi/2)=0
4. How many marks will I lose on the 9 marker for making an error at the very beginning of -k/root R rather than just k/root R? Absolutely hated that exam!
5. (Original post by Vip3rgt9)
That's for x.. Pi/2 gives you cosx = 0
6. (Original post by h2shin)
Stationary points for the trig: (pi/2, 1) (pi/6, 1.5) (5pi/6, 1.5)
Any agreements?

Oh and gradient to left was negative and gradient to right was positive so I put minimum but can't be too sure...
Wow I feel stupid, I worked out gradient to left is negative, and right was positive and wrote that was a turning point!
7. For 8i), the differential equation.

I got the correct answer but didn't leave it as

I took the root by power 3/2 of the things on the right hand side so I got

r = 2.87t + 1.94

Will that still be okay?
8. (Original post by JASApplications)
For 8i), the differential equation.

I got the correct answer but didn't leave it as

I took the root by power 3/2 of the things on the right hand side so I got

r = 2.87t + 1.94

Will that still be okay?
for some reason in the bracket I got 27 rather than 2.7 :s
9. (Original post by JASApplications)
For 8i), the differential equation.

I got the correct answer but didn't leave it as

I took the root by power 3/2 of the things on the right hand side so I got

r = 2.87t + 1.94

Will that still be okay?
I think you will have dropped one or two marks because if you multiplied (4.86t+2.7)^2/3 it wouldn't give you that?

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10. (Original post by JakePreedy)
I think that this would be okay because the question never specified what type of numbers "a" and "b" needed to be (i.e. rational, integer etc.) when in the form a ln(b).
Brilliant thankyou!

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11. would you lose marks for leaving ur intergrated answer in terms of u, I got the right answer as most people but I just didn't sub back what u was? I hope they aren't that harsh :L
12. (Original post by a10)
would you lose marks for leaving ur intergrated answer in terms of u, I got the right answer as most people but I just didn't sub back what u was? I hope they aren't that harsh :L
Actually, why do you have to sub it back in anyway? You've stated what u equals.
13. (Original post by Vip3rgt9)
EDIT: Cos(pi/2)=0
****, so iv lost 2 marks for not including the other two then
14. (Original post by a10)
can someone confirm this:

for the tan question my final integral was

and I subbed in values wrong for the first part so I ended up with

can someone confirm whether they got the -6+4 root 3 part?
Did exactly this. Integrated it wrong

Dunno how many marks we'll get, maybe 1 for 'putting limits in correctly'
and optimistically maybe 1 for 'using log rules correctly'
15. (Original post by zmai)
Thankyou!! I forgot to plug x values back in to find y values for question 4.

Would it be okay to write 1/2ln(root3) ? Did they specify the format?

Posted from TSR Mobile
I think you had to find the y-values but I doubt you'd lose more than 1 mark after finding the correct x-values.

I don't think they specified a format other than alnb so I think that would be fine
17. (Original post by zmai)
I think you will have dropped one or two marks because if you multiplied (4.86t+2.7)^2/3 it wouldn't give you that?

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It does. 2.7^2/3 = 1.94 and 4.86^2/3 = 2.87
18. Really struggled, it was so difficult! Everyone seems to be finding it okay gah
19. (Original post by Benjy100)
My money is on 62-63
How many marks do you think you got Ben?
20. (Original post by alastair999100)
Did exactly this. Integrated it wrong

Dunno how many marks we'll get, maybe 1 for 'putting limits in correctly'
and optimistically maybe 1 for 'using log rules correctly'
why is the integral wrong? I differentiated it and got the tan2x fraction?

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