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March 29, 2024, 05:30:27 am

Author Topic: VCE Specialist Maths 2 - 11/11/19 - Discussion/Questions/Solutions  (Read 17266 times)

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Macrophagee

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Re: VCE Specialist Maths 2 - 11/11/19 - Discussion/Questions/Solutions
« Reply #15 on: November 11, 2019, 07:12:17 pm »
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I found it quite difficult as well :(
Yeah was not expecting that 5 marker....

Massimooo123

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Re: VCE Specialist Maths 2 - 11/11/19 - Discussion/Questions/Solutions
« Reply #16 on: November 11, 2019, 07:13:33 pm »
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Very tough 5 marker I thought.... Also was very confused finding the area and volume for the vectors question. Rest was okay? My answers for the complex seemed a bit too basic, did anybody else just have parts of the quadratic formula for p and q?

I forgot what the area of a parallelogram was so I just did the side lengths multiplied by each other (which, upon reflection, is very clearly wrong lol).

I think for the volume one you had to find the middle of the parallelogram (the "centroid" according to google), find the distance between that and the peak of the pyramid which gives the height, then apply the formula V=(1/3)A*h. I obviously had the area of the base wrong, but if this method of finding the volume is correct and I did everything else right, would I get full marks? I still don't really get how answer marks and consequential marks work tbh.

AnonymooseUser

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Re: VCE Specialist Maths 2 - 11/11/19 - Discussion/Questions/Solutions
« Reply #17 on: November 11, 2019, 07:20:24 pm »
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So do people think the A+ cutoff will go down from 2018?

jkay__

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Re: VCE Specialist Maths 2 - 11/11/19 - Discussion/Questions/Solutions
« Reply #18 on: November 11, 2019, 07:39:41 pm »
+3
So do people think the A+ cutoff will go down from 2018?

Here's hoping. Holy, I think it'll even be as low as like 65/80, or even lower

This exam was, immeasurably and irrefutably FUCKED. That's the only way I can describe this abomination. It was the HARDEST out of the past 20 goddamn years of Specialist exams, and that is in no way an exaggeration. It was comparable to Kilbaha / MAV papers (not sure if that's a fair comparison, haven't done much of them), but that's how incredibly gone it was.

If you feel like you did badly, no worries. A lot of kids that go Melbourne High said that they messed up, very terribly
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S_R_K

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Re: VCE Specialist Maths 2 - 11/11/19 - Discussion/Questions/Solutions
« Reply #19 on: November 11, 2019, 08:36:33 pm »
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I think for the volume one you had to find the middle of the parallelogram (the "centroid" according to google), find the distance between that and the peak of the pyramid which gives the height, then apply the formula V=(1/3)A*h. I obviously had the area of the base wrong, but if this method of finding the volume is correct and I did everything else right, would I get full marks? I still don't really get how answer marks and consequential marks work tbh.

To get the height of the pyramid, I found the magnitude of the projection of AP onto the vector 6i + 2j + 5k (the vector from part d which is perpendicular to the parallelogram), this gave a pyramid volume of 24. (This is the point of finding a unit vector perpendicular to AB and AD).

Using one of the other corners of the base would have worked as well.
« Last Edit: November 11, 2019, 08:43:42 pm by S_R_K »

peds01

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Re: VCE Specialist Maths 2 - 11/11/19 - Discussion/Questions/Solutions
« Reply #20 on: November 11, 2019, 08:51:12 pm »
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Yeah I found this both of this year's exams much harder than most of the previous years exams I completed. Hopefully I did enough for a B on exam 1 and B+ on exam 2. Was looking at an A on both from my practice exams but oh well.

Massimooo123

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Re: VCE Specialist Maths 2 - 11/11/19 - Discussion/Questions/Solutions
« Reply #21 on: November 11, 2019, 08:58:02 pm »
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To get the height of the pyramid, I found the magnitude of the projection of AP onto the vector 6i + 2j + 5k (the where from part d which is perpendicular to the parallelogram), this gave a pyramid volume of 24. (This is the point of finding a unit vector perpendicular to AB and AD).

Using one of the other corners of the base would have worked as well.

That makes more sense than what I did, I don't know why I just forgot about that random-ass question and moved on like it was nothing. I think my height had a square root in it so things aren't looking good to say the least lol. I don't understand why my method would give a wrong height, but I guess it could just be a silly mistake. The peak of the pyramid would be directly above the intersection of the two lines AC and BD right (not directly above as in having a greater z coordinate in the xyz plane, but directly above as in perpendicular to the base of the pyramid)?

Ahh, this sucks. I keep thinking I'm doing well on my exams and then awakening to a harsh reality and I've still been surprised every time it's happened  :-[

Purple_Mango

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Re: VCE Specialist Maths 2 - 11/11/19 - Discussion/Questions/Solutions
« Reply #22 on: November 11, 2019, 09:02:06 pm »
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I think that should be right, checking with the normal volume in terms of y.
If that is it, then I'm pretty happy ! I just had the expanded version of it, so it should be fine, I guess.
And based off of other comments, looks like I messed up the volume of the pyramid. I got the height by getting the scalar product of the unit vector of 6i+2j+5k with whatever P was, instead of AP (or other vertex --> P). No wonder I got a weird volume.  :o

Although I found this exam difficult, personally, I consider MAV exams to be harder. 2019 MAV exam 2 especially bamboozled me
2018: Chemistry [45], Maths Methods [43]
2019: Biology [35], English [35], Japanese [32] :(, Specialist Maths [41], UMEP Chemistry [H2A], UCAT [83 percentile]
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tx inspire

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Re: VCE Specialist Maths 2 - 11/11/19 - Discussion/Questions/Solutions
« Reply #23 on: November 11, 2019, 09:13:18 pm »
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The A+ cut off was 66/80 in 2017 and 71/80 in 2018 so do you guys think it’ll be similar to 2017 again?

S_R_K

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Re: VCE Specialist Maths 2 - 11/11/19 - Discussion/Questions/Solutions
« Reply #24 on: November 11, 2019, 09:15:19 pm »
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I don't understand why my method would give a wrong height, but I guess it could just be a silly mistake. The peak of the pyramid would be directly above the intersection of the two lines AC and BD right (not directly above as in having a greater z coordinate in the xyz plane, but directly above as in perpendicular to the base of the pyramid)?

The peak of a pyramid is not necessarily vertically above the centroid of the base.

AlphaZero

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Re: VCE Specialist Maths 2 - 11/11/19 - Discussion/Questions/Solutions
« Reply #25 on: November 11, 2019, 09:31:35 pm »
+1
Solution are up!

Sorry for taking so long!
2015\(-\)2017:  VCE
2018\(-\)2021:  Bachelor of Biomedicine and Mathematical Sciences Diploma, University of Melbourne


mzhao

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Re: VCE Specialist Maths 2 - 11/11/19 - Discussion/Questions/Solutions
« Reply #26 on: November 11, 2019, 09:54:40 pm »
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Solution are up!

Sorry for taking so long!

Great work as always, AlphaZero!

I believe there should be one correction to Q2d:

"All complex solutions... have non-zero... imaginary parts"
So

will yield an imaginary number, which would make q complex, where q should instead be a real number.


is my answer. No need for absolute value within the sqrt, as from the first sentence of the question, we assume solutions always have a complex component, and hence, the discriminant is always negative.

EDIT:
clarified that I am considering the possibility of a modulus within the sqrt
and thanks Tau for pointing out that a in the denominator requires modulus
« Last Edit: November 11, 2019, 10:07:22 pm by mzhao »
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Tau

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Re: VCE Specialist Maths 2 - 11/11/19 - Discussion/Questions/Solutions
« Reply #27 on: November 11, 2019, 10:00:32 pm »
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Wouldn’t the modulus apply to the a in the denominator as well though?
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mzhao

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Re: VCE Specialist Maths 2 - 11/11/19 - Discussion/Questions/Solutions
« Reply #28 on: November 11, 2019, 10:01:58 pm »
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Wouldn’t the modulus apply to the a in the denominator as well though?

Sorry, I was referring to a potential absolute value within the sqrt.
But yes, that is a good pick up, will fix!
2016: Algorithmics [48 + Premier's Award]
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2018: Physics [50], Specialist [50 + Premier's Award]
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S_R_K

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Re: VCE Specialist Maths 2 - 11/11/19 - Discussion/Questions/Solutions
« Reply #29 on: November 11, 2019, 10:07:37 pm »
-1
Solution are up!

Sorry for taking so long!

Some preliminary comments:

Multiple choice, Question 4: i^1! = i, and both i^2! and i^3! = -1, then i^n! = 1, for all n ≥ 4, since n! is a multiple of 4 for all n ≥ 4. This gives i – 2 + 97*1.

Extended response 3a ii, I'm confused about your inequalities. I got, when 0 ≤ b < a, we have r > s (so that a – b > 0 and r/s > 1).

Extended response 6a. I think your calculation gives the chance of getting at least one sample with mean mass less than 370 or greater than 375. I did 1 – (1 – Pr(370 ≤ X ≤ 375))^2.

Otherwise, thanks again.