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# STEP III 2012 Discussion Thread Tweet

Maths exam discussion - share revision tips in preparation for GCSE, A Level and other maths exams and discuss how they went afterwards.

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1. Re: STEP III 2012 Discussion Thread
(Original post by Alexxh)
Done question 1 completely, (also got e^something for the second part :P)
oh and I don't think any information was missing! Although the phrasing of the question was certainly awkward...
I'm sure something was missing in Q1. The first expression is referred to as a 'result', and therefore needs something preceding it for it to have resulted from.

I'm also fairly sure that the missing first part was something very similar to

If z=(y^n) (dy/dx)^2, show that

The question is then about differential equations in y and x, for which we are using z as a substitution to help solve them and reach the form y=f(x)

for part (ii), i got the solution y=e^(0.5x^2) using the substitution

z=(1/y) (dy/dx)
2. Re: STEP III 2012 Discussion Thread
(Original post by Alexxh)
I think this is how I did part i) of question 1)
Does that seem right?

Solution to assumed version of Q1
Attached Files
3. 2012-III-1.pdf (202.3 KB, 451 views)
4. Last edited by MrDD; 30-06-2012 at 00:53.
5. Re: STEP III 2012 Discussion Thread
(Original post by MrDD)
yeuk

i'll post my solution again since people seem to be missing it

Solution to assumed version of Q1
Why do you make the assumption ? It follows from integrating the given expression wrt x;
(n=1)
... integrating by parts.... ...so .
6. Re: STEP III 2012 Discussion Thread
(Original post by Euclid)
Why do you make the assumption ? It follows from integrating the given expression wrt x;
(n=1)
... integrating by parts.... ...so .
just that i think that was intended to be a part of the question, but something went wrong at the printing stage

i've emailed them about this question, so hopefully we'll soon find out what was intended
7. Re: STEP III 2012 Discussion Thread
Answers to 2 and 5
Attached Files
8. Step2012Paper3Question2.pdf (59.0 KB, 264 views)
9. Step2012Paper3Question5.pdf (67.2 KB, 116 views)
10. (Original post by Euclid)
Why do you make the assumption ? It follows from integrating the given expression wrt x;
(n=1)
... integrating by parts.... ...so .
The reason that people think that there was a bit missing is not because the question was too hard but rather because the question was very blunt: they introduced z with no explanation, they didn't ask you to do anything with the first equation etc.

This was posted from The Student Room's iPhone/iPad App
11. Re: STEP III 2012 Discussion Thread
(Original post by LucasJ94)
Felt awful walking out of the exam, I normally like STEP III papers, but I'm good at calculus and the big trig questions, which there was none of :/.

I just want to stop thinking about this paper now, so can someone let me know how they think I did so I can have a bit of closure.

I only did 5 questions :/.

1 - Used n=1 and n=-2 on each part. And I built a relationship between z and y using the result they gave at the top. But I couldn't solve the equation I got for z in x, for either case. So barely any real progress.

3 - Drew all graphs, got up to the final show that equation, and couldn't do that, didn't state relevance to initial graphs.

5 - Completed.

7 - Up to the final summation, think my result for Z2(t) was wrong (looked a little too elaborate)

8 - Completed, but unsure of my result for the part about there being 2 values. I just found the second value and stated conditions on n, without any real proof or complete method.

How bad's the damage?
I don't like repeating myself, especially on forums. But I had another night of bad sleep due to this, it's eating up my time even now when I'm finished with it.

Can anyone give me some peace of mind? Whether it's a 3, 2 or 1, I just want to have a guide as to what I can expect so that hopefully I can stop caring until the day of results.

Thank you.
12. Re: STEP III 2012 Discussion Thread
(Original post by mikelbird)
Answers to 2 and 5
i don't think the last part of 5 is quite right, if you have SQRT(6) instead of SQRT(2) then you have a 6-rational point, not a 2-rational point.

Also, I think your second squared bracket should have a + in the middle, otherwise your sinhxcoshx terms don't cancel.

i think expanding (3coshx + SQRT(2)sinhx)^2 - (3sinhx + SQRT(2)coshx)^2 might work, although in the exam i used sec and tan instead of cosh and sinh
13. Re: STEP III 2012 Discussion Thread
(Original post by Rahul.S)
induction ofc could work....I decided to do a direct proof instead. They didnt mention a specific method so its fine.

your AEA should be S standard

oh yh how did your bredwin do?
AEA won't matter if Cambridge accept me I so hope I have done enough! Safmaster did very similar to me
14. Re: STEP III 2012 Discussion Thread
(Original post by hassi94)
I had to come back to say I did exact this Though I feel I dud well enough even if I get 0 on that one
they better award us somehow, I wasted a lot of time on that question But tbh, I think I have done enough for a 1 without it, so fingers crossed!
15. Re: STEP III 2012 Discussion Thread
(Original post by MrDD)
i don't think the last part of 5 is quite right, if you have SQRT(6) instead of SQRT(2) then you have a 6-rational point, not a 2-rational point.

Also, I think your second squared bracket should have a + in the middle, otherwise your sinhxcoshx terms don't cancel.

i think expanding (3coshx + SQRT(2)sinhx)^2 - (3sinhx + SQRT(2)coshx)^2 might work, although in the exam i used sec and tan instead of cosh and sinh
ooop!! you are quite right!!
16. Re: STEP III 2012 Discussion Thread
(Original post by MrDD)
yeuk

i'll post my solution again since people seem to be missing it

Solution to assumed version of Q1
Haha, got by accident, 19 marks?
Last edited by desijut; 29-06-2012 at 08:31.
17. Re: STEP III 2012 Discussion Thread
(Original post by Rahul.S)
I dont remember alot but it required a similar approach to the previous parts.
Yeah, i know that, but the locus was a lot more ****ed
18. Re: STEP III 2012 Discussion Thread
(Original post by MrDD)
yeuk

i'll post my solution again since people seem to be missing it

Solution to assumed version of Q1
I didn't miss your solution at all. I just thought as long as there isn't anything wrong with mine, there's no reason not to post it. Also, I find my method more straight forward..
19. Re: STEP III 2012 Discussion Thread
Ignore (silly mistake).
Attached Files
20. Step2012Paper3Question5.pdf (66.8 KB, 40 views)
21. Last edited by mikelbird; 29-06-2012 at 08:54. Reason: mistake
22. Re: STEP III 2012 Discussion Thread
This time i will get it right!!!! (All I can say is dont try and do mathematics if you have insomnia or have been drinking (or both)!!!
Attached Files
23. Step2012Paper3Question5.pdf (67.4 KB, 127 views)
24. Last edited by mikelbird; 29-06-2012 at 14:05. Reason: correction
25. (Original post by mikelbird)
This time i will get it right!!!!
I knew I was doing something wrong when working on this last night. The reasons why doing maths at 2am is a bad idea after an evening of jitsu.

On my way home, will get some solutions out and latex if they are not up yet

This was posted from The Student Room's iPhone App
26. Re: STEP III 2012 Discussion Thread
(Original post by maksokio)
how many marks do you guys think I will get for doing the whole of question 7 except part (iii)?
could someone help with with that?
27. Re: STEP III 2012 Discussion Thread
(Original post by maksokio)
how many marks do you guys think I will get for doing the whole of question 7 except part (iii)?
Maybe about 12. It was the hardest part of the question so I think it will worth 7-9 marks. But nobody knows...
28. Re: STEP III 2012 Discussion Thread
Here's a solution to question 8.

Spoiler:
Show

Last edited by B Jack; 29-06-2012 at 10:54. Reason: slight mistake :P
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