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# WJEC C3/C4 8th/17th June 2016 watch

1. (Original post by IrrationalRoot)
I'm not entirely sure whether my answers are correct, the first equation was something like
3cosecT(cosecT-1)=cot^2 T + some constant, can you remember what the eqn was?

EDIT: LaTeX is being stupid so I wrote it without, T being theta.
It was 3cosecT(cosecT - 1) = 5cot^2 T - 9. I think I realise my error now - I expanded the bracket to 3cosec^2 T - 3 instead of 3cosec^2 T - 3cosecT. Six marks down the drain. I'm not getting follow through marks for that, am I?
2. (Original post by caitanna98)
what is 57/75 in UMS?
Impossible to say for certain but I'd imagine it would be a low A/high B.
3. (Original post by Hydeman)
It was 3cosecT(cosecT - 1) = 5cot^2 T - 9. I think I realise my error now - I expanded the bracket to 3cosec^2 T - 3 instead of 3cosec^2 T - 3cosecT. Six marks down the drain. I'm not getting follow through marks for that, am I?
Ah that's an unfortunate mistake (well done remembering the eqn though ).
I would think it extremely harsh to not give any marks but maybe that's how the ms works I'm not sure.
When you solved the quadratic did you get integer solutions? If not did you maybe suspect you had the wrong quadratic? It almost always factorises nicely.

Also did you get the right answers for (b)?
4. (Original post by Mango88)
What values did you get for a and b in the transformations question?

Youre going to feel as gutted as me because I got the counter example wrong.
(+a) means shift right with -a to x coordinates. Therefore its just the x coodinates of the points of intersection with x-axis
a=-3,5

For bf(x). Its -6/4 giving you b=-2/3 using the minimum point
5. (Original post by Maths is Life)
I reckon it will be as low as last years. Although for some reason there was no proof or trigonometric graph sketching. Spent so much effort on them...
There was a proof by counterexample question though.

(Original post by Maths is Life)
Could you help me with the circle question and counter example?
I didn't attempt part a) of the circles question because I literally couldn't remember anything from C2. Part b) was a recurrence relations question - I could explain it to you, but I can't remember the equation exactly...

Counterexample: I said let a = 2, b = 3, c = 6 and d = 6. With these values, as the question states, a = 2 is a factor of c = 6, and b = 3 is a factor of d = 6, but if you worked out a + b (2 + 3 = 5) and c + d (6 + 6 = 12), it turns out that (a + b) is not a factor of (c + d) because 5 is not a factor of 12.

(Original post by Maths is Life)
Youre going to feel as gutted as me because I got the counter example wrong.(+a) means shift right with -a to x coordinates. Therefore its just the x coodinates of the points of intersection with x-axisa=-3,5For bf(x). Its -6/4 giving you b=-2/3 using the minimum point
Don't worry about it. It was only two marks. I got the whole of question 2 wrong...
6. (Original post by IrrationalRoot)
Ah that's an unfortunate mistake (well done remembering the eqn though ).
I would think it extremely harsh to not give any marks but maybe that's how the ms works I'm not sure.
When you solved the quadratic did you get integer solutions? If not did you maybe suspect you had the wrong quadratic? It almost always factorises nicely.
Thanks. I hope there are some marks for correct working.
Thing is, I didn't get a quadratic, and so there weren't two solutions - I got something like -2cot2T = -9, which gave something tan2T = 2/9, which only gave two values of T. :/ Yeah, I don't think I'll get marks for that. Nerves got the better of me, I suppose.

Also, I did know it was wrong, but I couldn't work out where I'd done wrong (for some reason I didn't suspect the very first step at all, reading over and over again the subsequent ones in search of an error), so I just left it like that.

Also did you get the right answers for (b)?
Nope. I'd seen a question like (b) on a 2014 paper, I think, but I couldn't for the life of me remember how to do it. So, worst case scenario, I'll get 60/75. Hopefully that's still a mid-level A.

What do you think the grade boundaries might be like? I seem to be in a minority in having found that as hard as/harder than last year's paper.
7. if you get the workings right but wrong numbers how many marks do u lose
8. (Original post by Hydeman)
There was a proof by counterexample question though.

I didn't attempt part a) of the circles question because I literally couldn't remember anything from C2. Part b) was a recurrence relations question - I could explain it to you, but I can't remember the equation exactly...

Counterexample: I said let a = 2, b = 3, c = 6 and d = 6. With these values, as the question states, a = 2 is a factor of c = 6, and b = 3 is a factor of d = 6, but if you worked out a + b (2 + 3 = 5) and c + d (6 + 6 = 12), it turns out that (a + b) is not a factor of (c + d) because 5 is not a factor of 12.

Don't worry about it. It was only two marks. I got the whole of question 2 wrong...
If youve read my previous posts you should know that Im resitting and by doing the circle show that and a silly 2 marker wrong I wont be getting that 100 UMS resitters are expected to get
9. (Original post by Maths is Life)
If youve read my previous posts you should know that Im resitting and by doing the circle show that and a silly 2 marker wrong I wont be getting that 100 UMS resitters are expected to get
Expected by whom? University offers are based on grades, so 200 UMS across C3 and C4 is no better than 180 UMS; they're both A*s. Besides, if those were the only two things you got wrong, and the boundaries don't change much from last year, you will end up with 100 UMS.
10. (Original post by caitanna98)
if you get the workings right but wrong numbers how many marks do u lose
By workings you mean method marks. So yeah youll get them just not answer marks. Right method generally leads to right answer. Always double check answers I tell myself. For Q2 I only realised that I didnt square root the other side😂 So I quickly corrected that
11. (Original post by Hydeman)
Expected by whom? University offers are based on grades, so 200 UMS across C3 and C4 is no better than 180 UMS; they're both A*s. Besides, if those were the only two things you got wrong, and the boundaries don't change much from last year, you will end up with 100 UMS.
You couldnt be more right - why not aim for 100UMS. A lot of people say they would love to boast about the elusive 600UMS 😂👍
12. Hi all, do you think the grade boundaries will be higher or lower than last year's? Also, i got 1/y^3 for q4 part 2, when the answer should be -1/y^3. How many marks would i lose for this?
13. (Original post by Hydeman)
Thanks. I hope there are some marks for correct working.
Thing is, I didn't get a quadratic, and so there weren't two solutions - I got something like -2cot2T = -9, which gave something tan2T = 2/9, which only gave two values of T. :/ Yeah, I don't think I'll get marks for that. Nerves got the better of me, I suppose.

Also, I did know it was wrong, but I couldn't work out where I'd done wrong (for some reason I didn't suspect the very first step at all, reading over and over again the subsequent ones in search of an error), so I just left it like that.

Nope. I'd seen a question like (b) on a 2014 paper, I think, but I couldn't for the life of me remember how to do it. So, worst case scenario, I'll get 60/75. Hopefully that's still a mid-level A.

What do you think the grade boundaries might be like? I seem to be in a minority in having found that as hard as/harder than last year's paper.
When in doubt with trig equations, (I know this is late but might help for C4) remember that sine and cosine are the only 'real' trig functions. The 'others' are just combinations of them and should be viewed as such. So with (b) you convert to sines and cosines and you get a couple of fractions, then it's natural to clear the fractions and you get some equation for tan (I believe tan(phi)=-2/3).

Well I haven't done many papers at all so not very familiar with GBs/the standard difficulty of papers, although I checked last years and I think they'll be a bit lower than last years since there were a couple of trickier things but I may be wrong.

Dw though, just do well in C4, remember how ridiculously low the C4 GBs were last year (I believe 80% for 100UMS!)?
14. (Original post by Hi:))
Is there an unofficial mark scheme up yet?
Look at post 89 for an unofficial ms but the latex stopped working at the end so it's a bit tough to read.
15. (Original post by IrrationalRoot)
When in doubt with trig equations, (I know this is late but might help for C4) remember that sine and cosine are the only 'real' trig functions. The 'others' are just combinations of them and should be viewed as such. So with (b) you convert to sines and cosines and you get a couple of fractions, then it's natural to clear the fractions and you get some equation for tan (I believe tan(phi)=-2/3).
Thanks, I'll remember that for C4!
Well, I did rewrite it as 2/(sinx) + 3(cosx) but couldn't devote any more time to it. Oh well.

Well I haven't done many papers at all so not very familiar with GBs/the standard difficulty of papers, although I checked last years and I think they'll be a bit lower than last years since there were a couple of trickier things but I may be wrong.

Dw though, just do well in C4, remember how ridiculously low the C4 GBs were last year (I believe 80% for 100UMS!)?
Haha, though it was also commensurately difficult. Thanks for making me feel better about it.
16. (Original post by Firestartc)
Hi all, do you think the grade boundaries will be higher or lower than last year's? Also, i got 1/y^3 for q4 part 2, when the answer should be -1/y^3. How many marks would i lose for this?
I thought it was -sec^2(y/2)/8
17. I also didn't get -1/y3 for the last part of question 4. C4 will have to be really good.
18. Also, can someone post the answers for the integrations questions? I can't find them (tbh can't rly remember how many there were) but i think there was an integration only section like the differentiation only section or was the only integration question the one with answer a =2.3???
19. I reckon I got around 65-67. Would that be an A*?
20. (Original post by Firestartc)
Also, can someone post the answers for the integrations questions? I can't find them (tbh can't rly remember how many there were) but i think there was an integration only section like the differentiation only section or was the only integration question the one with answer a =2.3???
There was an integration-only section. The one with a = 2.3 was the definite integration, but there were three indefinite integration questions before that.

(Original post by elliekmorgan62)
I reckon I got around 65-67. Would that be an A*?
Probably, but it can't be said for certain.

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