Carrotsticks' MX2 HSC 2013 Solutions (2 Viewers)

[hayabusaboston]

>slightly messed up
>will I get 3/3

what do you think

Maybe my mess up wasn't bad, and maybe the shape is rite? Idk I put asymptotes at the same values as carrot, and drew as carrot did ok, I just remember putting the initial part of the graph on the left thru (1,0). Will I lose one for that?

 

[RealiseNothing]

Maybe my mess up wasn't bad, and maybe the shape is rite? Idk I put asymptotes at the same values as carrot, and drew as carrot did ok, I just remember putting the initial part of the graph on the left thru (1,0). Will I lose one for that?

Well your graph isn't right then?

 

[hayabusaboston]

Well your graph isn't right then?

k 1 mark off then u'd say? ITS SAME SHAPE PLZ, AND SAME ASYMPTOTES

 

[hayabusaboston]

and yea, do I get 3/4 for e^x volumes for a carried on error like replacing 4 with 3?

 

[RealiseNothing]

and yea, do I get 3/4 for e^x volumes for a carried on error like replacing 4 with 3?

Yep 3/4.

 

[Makematics]

Fk i would usually be able to scab a mark for the volumes q if it were a school exam. Not this time

 

[jyu]

Can any one explain Q12diii?

 

[seanieg89]

Can any one explain Q12diii?

there is no q12diii.

 

[RealiseNothing]

there is no q12diii.

yes there is?

 

[seanieg89]

yes there is?

Really? Not in the version I have, they must have changed the numbering of things. There is no q12d at all in mine.

Edit: Oh right, this isn't bos trials .

 

[RealiseNothing]

Really? Not in the version I have, they must have changed the numbering of things. There is no q12d at all in mine.

It's the "Prove that BC is parallel to PQ" question.

 

[Makematics]

guys i have a question. for the 4 mark volumes, i never like to 'unroll' the shell into a rectangular prism. instead i like to derive the result from fresh using subtraction of the inner and outer radii. when applying this method today, i forgot the height of the shell, and as a result there was no e^x present in my integral AT ALL. how many marks will i lose for it? it's an absolutely terrible mistake, i know...

ended up on 0/4 for this Q. A warning to all students, BE VERY CAUTIOUS WHEN USING ALTERNATIVE METHODS. I also got 1/3 on another Q despite my solution being 100% valid, because I intuitively used a different method to the one they would have liked.

Not too sure if you can get marks even.... but then again I'm not sure.

spot on as usual, RoT

dudeee i will get some marks haha, definitely for at least getting an expression and integrating it.

nope

 

[Carrotsticks]

ended up on 0/4 for this Q. A warning to all students, BE VERY CAUTIOUS WHEN USING ALTERNATIVE METHODS. I also got 1/3 on another Q despite my solution being 100% valid, because I intuitively used a different method to the one they would have liked.




spot on as usual, RoT


nope

Did you order your actual paper, or just the raw marks?

Usually, when you get 0 for a solution that was 'almost complete' except one expression was missing, it is because that missing expression made the question substantially easier to do.

Also, what was the Q you got 1/3 on, and what method did you use?

 

[Makematics]

Did you order your actual paper, or just the raw marks?

Usually, when you get 0 for a solution that was 'almost complete' except one expression was missing, it is because that missing expression made the question substantially easier to do.

Also, what was the Q you got 1/3 on, and what method did you use?

Just the raw marks. Yeah, I know that I oversimplified the question, but at school we have always been told that we would get at least some marks.
I got 1/3 on 15(a)
On your solutions you use mod-arg form to get the answer.
All I did was let z=x+iy and w=a+ib, and then found the area A of the triangle using 1/2 absinC. Finding the area was somewhat troublesome, but it still worked out for me.

 

[seanieg89]

It would be cool if people could volunteer to upload their papers on a thread here, for the benefit of future students to see how many marks various partial solutions and mistakes are worth.

 

[Carrotsticks]

Just the raw marks. Yeah, I know that I oversimplified the question, but at school we have always been told that we would get at least some marks.
I got 1/3 on 15(a)
On your solutions you use mod-arg form to get the answer.
All I did was let z=x+iy and w=a+ib, and it worked out nicely for me.

How did you work out the area of the triangle OZW with Z(x,y) and W(a,b) ? Only fast way I can think of doing is using the determinant of a 2x2, otherwise that would take a pretty long time?

It would be cool if people could volunteer to upload their papers on a thread here, for the benefit of future students to see how many marks various partial solutions and mistakes are worth.

That really would, and it would also educate a lot of the teachers on how marking works in the HSC, because to put it quite bluntly too few of them actually know how it works.

If they all did, then students would no longer need to write those ridiculous conclusions after each induction problem.

 

[Makematics]

How did you work out the area of the triangle OZW with Z(x,y) and W(a,b) ? Only fast way I can think of doing is using the determinant of a 2x2, otherwise that would take a pretty long time?

Ok so after redoing the question I realise that it was far from quick and from from elegant, but surely it is mathematically correct?

 

[Makematics]

Bump. Is my solution valid?

 

[Carrotsticks]

Bump. Is my solution valid?

You said that the arg was inverse tan ....

Are you sure this is always true?

 

[Makematics]

You said that the arg was inverse tan ....

Are you sure this is always true?

wait why isn't it? Sorry i've forgotten a lot over the past two months hahaha