q4 biased toward 4 unit (1 Viewer)

[100percent]

justchillin is a math dude, not word smith

 

[Jaydels]

I used reverse chain rule... [f(x)]^n[f'(x)]=[f(x)]^n+1/n+1

 

[justchillin]

Dont embarrase urself by correcting me... I was talking about the chain rule in the differentiation of the thing to be integrated...

 

[haboozin]

yea mate calm down, justchillin does love himself - but after all he does know what he is talking about...
its actually in the syllabus for you to be able to know how things differentiate things to get its integral...

and thats what he was doing - clearly...

anyways,
not only is that in the syllabus - another thing is t results...

messy but possible..

just because they learn more about it in 4unit doesnt mean they were biased...

 

[DRAGONZ]

Dont embarrase urself by correcting me... I was talking about the chain rule in the differentiation of the thing to be integrated...

When you think about it, it's quite an anomaly that in order to directly apply the 'reverse chain rule', you need to apply the 'chain rule' to the integrand. Hehe.

In the exam, I just went:

int. cosx(sinx)^2 dx = [(sinx)^3]/3 ---> By Reverse Chain Rule
= etc etc.

I'm sure that'll be fine for the full marks, but then perhaps I get an old-fashioned marker who doesn't like a show of 'arrogance' like that ... I dunno.

 

[香港!]

^
i just wrote
int. cosxsin^2x dx=int. sin^2 x d(sinx)=sin³x\3+C
i hope that will give me full marks lol

 

[_dhj_]

Isn't that how you're supposed to do it?

 

[DRAGONZ]

^
i just wrote
int. cosxsin^2x dx=int. sin^2 x d(sinx)=sin³x\3+C
i hope that will give me full marks lol

I really hope, for your sake, that you DIDN'T do that.

The integral had limits ... in which case, I hope that you just forgot that it had limits when you wrote your explanation two minutes ago.

And hey Daniel! How'd you go, mate? Adam says he didn't get over 80 ... what's the world coming to at our school?!? And Jonathan's hopes of 84 were dashed because he totally missed the induction question .. he didn't see it.

Oh well. There's still at least another 10 or 15 people who I can think of at school who could conceivably get 82, 83 or 84. I'm still so annoyed about the amount of time I spent on the one probability question. I would've had 82 otherwise, because I ran out of time

 

[香港!]

^ oh ya i did put the limits in.. whew!
I hope I did put it in correctly though lol

 

[_dhj_]

I really hope, for your sake, that you DIDN'T do that.

The integral had limits ... in which case, I hope that you just forgot that it had limits when you wrote your explanation two minutes ago.

And hey Daniel! How'd you go, mate? Adam says he didn't get over 80 ... what's the world coming to at our school?!? And Jonathan's hopes of 84 were dashed because he totally missed the induction question .. he didn't see it.

Oh well. There's still at least another 10 or 15 people who I can think of at school who could conceivably get 82, 83 or 84. I'm still so annoyed about the amount of time I spent on the one probability question. I would've had 82 otherwise, because I ran out of time

I did alrite but I found it pretty hard. Hopefully 75+ if stupid mistakes are kept to a minimum.

And wth Adam got under 80?? are you serious??

Ah well there goes our chances of getting a 100 uai

 

[Raginsheep]

Sif adam needs 3u. It proabaly won't even count for him unless he's doing 10 units...

 

[_dhj_]

As if not.. 3u is like the easiest subject to get a high scaled mark in...

 

[MarsBarz]

You know what's funny? Just one or two days before the extension examination, someone posted a thread in the maths forum with that same integral. Had I not read that thread at 3AM the day of the exam I would probably not have known how to do that question haha.

So thanks to whoever it was that posted it in the maths forum. You my friend, helped me gain some easy marks .

 

[香港!]

You know what's funny? Just one or two days before the extension examination, someone posted a thread in the maths forum with that same integral. Had I not read that thread at 3AM the day of the exam I would probably not have known how to do that question haha.

So thanks to whoever it was that posted it in the maths forum. You my friend, helped me gain some easy marks .

edit: here it is
http://community.boredofstudies.org/showthread.php?t=90167

 

[DRAGONZ]

Sif adam needs 3u. It proabaly won't even count for him unless he's doing 10 units...

Well he's not doing 10 units ..

He does 4 Math, 3 English, 3 Latin, and one of Phys/Chem. So 12.

Either way, internally he was top 5 for every single subject, I think.

A 97 or 98 in 3-unit math doesn't mean he can't get 100 UAI. I'm pretty sure his raw mark for English was something around 58 or 59 / 60 ... Sudeep also reckons that he totally pwned English (I think he said something about possibly getting 60/60?).

I don't think Adam will go too bad in the rest of his subjects ... he has EX1 tomorrow, and it seems that like the top 10 guys who do that all seemingly get 100% in everything.

So he can still get 100 UAI ... I hope NSB PRIDE!

I wonder how we went as a grade in 3 unit and 4 unit ... because we came second to Ruse last year for MX2. Twould be good to repeat that.

 

[香港!]

^ hey Dragonz, u remember Felix back in yr 10?
he was there topping eng. ext. 1 i think, den left..
hehe

 

[nick1048]

and I object to the anti-4unit sentiment in this forum. We do more work than you, thus our marks are better, period.

suck my dick, 4u <> more work. You don't get better marks because you work harder, you get stereotypically better marks because your exposure to mathematics is considerably greater and thus your focus less shared amongst other subjects relative to a 3u student. The BOS doesn't go ohhh the 4u kids do more work, here lets chuck in a 4u question buddy... get over yourself.

 

[icycloud]

Alternative method without substitution or "reverse" chain rule: http://community.boredofstudies.org/showpost.php?p=1975263&postcount=13

 

[icycloud]

icycloud, are you going to do all that just for 2 marks? I don't think so.

Of course not, because I know the substitution method. However, I just wanted to show that you can use a "3U only" method to solve this integral, that is all .

 

[Captain pi]

jarro_2783's teacher is correct.

Page 66 of the 3 unit syllabus says "In all examples the substitution is to be given."

http://www.boardofstudies.nsw.edu.au/syllabus_hsc/pdf_doc/maths23u_syl.pdf

That is incorrect. The syllabus has different allowances for integration of trigonometric functions. I refer you to page 71 of the syllabus where, amazingly, an example of what integrals should be able to be completed by 3U students is the exact question in the exam is given

In essence, 3U students should be able to integrate integrands of the form sin^n(x)·cos(x) and cos^n(x)·sin(x). The method they use is up to them; but, as substitution is the easiest, that is the one that is implied in the syllabus.