OCR C4 (not mei) 18th June 2013 revision

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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!

Reply 601

h2shin

Original post by Vip3rgt9

...Forgot about the limits.

That's for x.. Pi/2 gives you cosx = 0

Reply 602

Alex Newton

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! :angry:

Reply 603

JASApplications

For 8i), the differential equation.

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

Unparseable latex formula:

\[r]

Instead, when I got to

Unparseable latex formula:

\[{r^{\frac{3}{2}}}\ = (4.86t + 2.7)

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?

Reply 604

Alex Newton

Original post by JASApplications

For 8i), the differential equation.

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

Unparseable latex formula:

\[r]

Instead, when I got to

Unparseable latex formula:

\[{r^{\frac{3}{2}}}\ = (4.86t + 2.7)

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

Reply 605

zmai

Original post by JASApplications

For 8i), the differential equation.

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

Unparseable latex formula:

\[r]

Instead, when I got to

Unparseable latex formula:

\[{r^{\frac{3}{2}}}\ = (4.86t + 2.7)

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?

Posted from TSR Mobile

Reply 606

zmai

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!

Posted from TSR Mobile

Reply 607

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

Reply 608

Vip3rgt9

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.

Reply 609

a10

Original post by Vip3rgt9

...Forgot about the limits.
EDIT: Cos(pi/2)=0

****, so iv lost 2 marks for not including the other two then :s-smilie:

Reply 610

alastair999100

Original post by a10

can someone confirm this:

for the tan question my final integral was

-2ln(2- sec^2(x))

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

(-2 ln 2/3) + 2ln(-6+4root 3)

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'

Reply 611

Benjy100

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

Reply 612

SJ12345

A* grade boundary anyone?

Reply 613

JASApplications

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?

Posted from TSR Mobile

It does. 2.7^2/3 = 1.94 and 4.86^2/3 = 2.87

Reply 614

LydBarry

Really struggled, it was so difficult! Everyone seems to be finding it okay gah

Reply 615

Theo115

Original post by Benjy100

My money is on 62-63

How many marks do you think you got Ben?

Reply 616

a10

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?