STEP III 2012 Discussion Thread

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 think this is how I did part i) of question 1)
Does that seem right?

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 $z=y^n(\frac{dy}{dx})^2$? It follows from integrating the given expression wrt x;
(n=1)
$\frac{dz}{dx}=\frac{dy}{dx}[(\frac{dy}{dx})^{2}+2y\frac{d^{2}y}{dx^{2}}]$... integrating by parts.... $\int(\frac{dy}{dx})^{3}{dx}={y}(\frac{dy}{dx})^{2}-\int{2y}\frac{dy}{dx}\frac{d^{2}y}{dx^{2}}{dx}$...so $z=y(\frac{dy}{dx})^2$.

Why do you make the assumption $z=y^n(\frac{dy}{dx})^2$? It follows from integrating the given expression wrt x;
(n=1)
$\frac{dz}{dx}=\frac{dy}{dx}[(\frac{dy}{dx})^{2}+2y\frac{d^{2}y}{dx^{2}}]$... integrating by parts.... $\int(\frac{dy}{dx})^{3}{dx}={y}(\frac{dy}{dx})^{2}-\int{2y}\frac{dy}{dx}\frac{d^{2}y}{dx^{2}}{dx}$...so $z=y(\frac{dy}{dx})^2$.

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?

Answers to 2 and 5

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?

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

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

yeuk

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

Solution to assumed version of Q1

I dont remember alot but it required a similar approach to the previous parts.

yeuk

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

Solution to assumed version of Q1

This time i will get it right!!!!

how many marks do you guys think I will get for doing the whole of question 7 except part (iii)?

how many marks do you guys think I will get for doing the whole of question 7 except part (iii)?