HSC 2013-14 MX1 Marathon (archive) (2 Viewers)

[hayabusaboston]

Re: HSC 2013 3U Marathon Thread

Doesn't mean I've tried it.

Icic

OK u will likely get it, perms and combs one of ur favourites eh?

 

[Sy123]

Re: HSC 2013 3U Marathon Thread

There is a fault in your question.

And I only just got to look at this question now.

edit: I wasn't thinking properly and made a mistake, I was confused with the conditions and I thought that the team couldn't play in some conditions but I see you resolved that in your question, so yes there is no mistake

Ok I'll try with this attempt, first name the conditions in the question, (1) and (2).

There then initiates four cases that we only observe for Defense (D) and Forwards (F)

It's possible to do this because your conditions don't make sense if they apply for people among different lines.









We will simply ignore all arrangements for goalies, I'll multiply my answer by arranging defence and forward by 2 at the end.

Case 1:



Case 2:



Case 3:



Case 4:




So my final answer is:

10808

Is it? It might be wrong because I'm quite weak with permutations and combinations.

Well if there's a fault, naturally you would have mentioned what the fault was. Since u havent, we can all assume u are making shit up.

Lol man its called a mistake, I thought the way the conditions were layed out a team could not be constructed in some cases.
Nevertheless I still had a go and it might be wrong but at least I tried.

 

[Carrotsticks]

Re: HSC 2013 3U Marathon Thread

Just deleted more posts than I should have. Keep it civil please =)

 

[Makematics]

Re: HSC 2013 3U Marathon Thread

As i asked before, haya did you make the question?

 

[Makematics]

Re: HSC 2013 3U Marathon Thread

i get sqrt (1+sin2x) +c but idk if this is corect, rushed it a bit. if it's correct i shall tex it up hopefully.

 

[Sy123]

Re: HSC 2013 3U Marathon Thread

i get sqrt (1+sin2x) +c but idk if this is corect, rushed it a bit. if it's correct i shall tex it up hopefully.

That isn't correct.

 

[Makematics]

Re: HSC 2013 3U Marathon Thread

That isn't correct.

awww damn. i let sin2x=sin ^2 theta and then proceeded ... what/how did you do?

 

[hayabusaboston]

Re: HSC 2013 3U Marathon Thread

There is a fault in your question.

And I only just got to look at this question now.

edit: I wasn't thinking properly and made a mistake, I was confused with the conditions and I thought that the team couldn't play in some conditions but I see you resolved that in your question, so yes there is no mistake

Ok I'll try with this attempt, first name the conditions in the question, (1) and (2).

There then initiates four cases that we only observe for Defense (D) and Forwards (F)

It's possible to do this because your conditions don't make sense if they apply for people among different lines.









We will simply ignore all arrangements for goalies, I'll multiply my answer by arranging defence and forward by 2 at the end.

Case 1:



Case 2:



Case 3:



Case 4:




So my final answer is:

10808

Is it? It might be wrong because I'm quite weak with permutations and combinations.

Idk if thats right, I got 7800 or something, but yea I wasnt 100% sure so maybe someone else can confirm.

 

[Makematics]

Re: HSC 2013 3U Marathon Thread

so i guess u didnt make it then

 

[hayabusaboston]

Re: HSC 2013 3U Marathon Thread

so i guess u didnt make it then

Hey when u make a question u still have to figure out the answer lol.

 

[HeroicPandas]

Re: HSC 2013 3U Marathon Thread

awww damn. i let sin2x=sin ^2 theta and then proceeded ... what/how did you do?

This commonly neglected identity will unleash its power in this question

 

[anomalousdecay]

Re: HSC 2013 3U Marathon Thread

I am not saying that you are wrong in any way at all, but why did wolfram integrator answer it like this?

 

[RealiseNothing]

Re: HSC 2013 3U Marathon Thread

 

[seanieg89]

Re: HSC 2013 3U Marathon Thread

and then? .

 

[anomalousdecay]

Re: HSC 2013 3U Marathon Thread

Why did this happen. It looks like realise nothing is right but for some reason the wolfram integrator says otherwise.

 

[Makematics]

Re: HSC 2013 3U Marathon Thread

Hmmm I don't get why my way is wrong though? :S Everything works out rlly nicely to get my answer

 

[seanieg89]

Re: HSC 2013 3U Marathon Thread

Why did this happen. It looks like realise nothing is right but for some reason the wolfram integrator says otherwise.

View attachment 28145

Both wolfram alpha and realisenothing aren't entirely correct. This sort of integral is really awkward to find an indefinite integral valid over the whole real line (if it is even possible).

Actually I suppose it probably is, using floor/ceiling functions, but yeah its not nice.

 

[anomalousdecay]

Re: HSC 2013 3U Marathon Thread

Both wolfram alpha and realisenothing aren't entirely correct. This sort of integral is really awkward to find an indefinite integral valid over the whole real line (if it is even possible).

Actually I suppose it probably is, using floor/ceiling functions, but yeah its not nice.

I did something before which is just the pure original integration rule. I got something like:




This is still wrong as we must consider what if :




But this is just using the rule where you divide by the derivative of the substitution (u = 1-sin2x) and the new power.

 

[anomalousdecay]

Re: HSC 2013 3U Marathon Thread

I guess the reason why it happened is because you can't take the square root of trig. functions without regarding absolute values?

 

[seanieg89]

Re: HSC 2013 3U Marathon Thread

I guess the reason why it happened is because you can't take the square root of trig. functions without regarding absolute values?

The insides being trigonometric has nothing to do with it, it is just that

.