# BoS Maths Trials 2019 (1 Viewer)

#### realandbounded

##### New Member
I heard the guy who came top is really the person controlling Sharky behind the scenes...

#### sharky564

##### Member
I heard the guy who came top is really the person controlling Sharky behind the scenes...
We're actually identical twins uh what?

#### psmao

##### Member
When will we get our 3u results back?

#### englishessayssuck

##### New Member
WOoOoWwowowoww someone GOT 80????!?!?!?!

ok jokes aside, sup guys I'm "englishessayssuck" (mirroring my then-profound disdain for writing english essays like 3 years ago) and my student code for the bos trials was 3705 (so yeah I got the 80).

Anyway so yeah I personally found the Bos trials this year quite challenging compared to the one last year, which I finished on time apart from q11a (at home of course), so when I challenged my boi Sharky in getting 100 for the 2019 edition I was somewhat confident I could get rather close to that score (which turned out wasn't to be). I guess when I started the paper, q11 kinda already bombed out because q11a was written by none other than Sharky and Paradoxica (ended up not getting anything), and a combination of typos and my incompetence meant out of what should have been an easy 12 marks for q11, I only managed to convert 8 of them. However, apart from skipping a few 2-3 markers along the way throughout the rest of the exam which I felt would take too much time for the number of marks it was worth, the rest of the paper was somewhat manageable, if a little demanding on time.

For those people who are surprised about someone getting 80, I believe it's definitely possible for someone in the future to climb quite a bit higher into perhaps mid-85 range, and I don't expect the 80 record to stay for too long before someone eventually exceeds that score.

if you guys have any questions then you can post something below or send a message but I probably won't answer much because I'm a very irregular user of this website (and definitely don't mention about the test yesterday)

once again thanks to the people who made the BoS trials possible this year and I hope to possibly work with some of you in making an even harder 4u test next year.

bye

#### realandbounded

##### New Member
WOoOoWwowowoww someone GOT 80????!?!?!?!

ok jokes aside, sup guys I'm "englishessayssuck" (mirroring my then-profound disdain for writing english essays like 3 years ago) and my student code for the bos trials was 3705 (so yeah I got the 80).

Anyway so yeah I personally found the Bos trials this year quite challenging compared to the one last year, which I finished on time apart from q11a (at home of course), so when I challenged my boi Sharky in getting 100 for the 2019 edition I was somewhat confident I could get rather close to that score (which turned out wasn't to be). I guess when I started the paper, q11 kinda already bombed out because q11a was written by none other than Sharky and Paradoxica (ended up not getting anything), and a combination of typos and my incompetence meant out of what should have been an easy 12 marks for q11, I only managed to convert 8 of them. However, apart from skipping a few 2-3 markers along the way throughout the rest of the exam which I felt would take too much time for the number of marks it was worth, the rest of the paper was somewhat manageable, if a little demanding on time.

For those people who are surprised about someone getting 80, I believe it's definitely possible for someone in the future to climb quite a bit higher into perhaps mid-85 range, and I don't expect the 80 record to stay for too long before someone eventually exceeds that score.

if you guys have any questions then you can post something below or send a message but I probably won't answer much because I'm a very irregular user of this website (and definitely don't mention about the test yesterday)

once again thanks to the people who made the BoS trials possible this year and I hope to possibly work with some of you in making an even harder 4u test next year.

bye
WOW THAT IS SO COOL!!!

Is it true you were on the Australian olympiad team as well? What's harder, 4u or the international olympiad?

#### akkjen

##### Active Member
WOoOoWwowowoww someone GOT 80????!?!?!?!

ok jokes aside, sup guys I'm "englishessayssuck" (mirroring my then-profound disdain for writing english essays like 3 years ago) and my student code for the bos trials was 3705 (so yeah I got the 80).

Anyway so yeah I personally found the Bos trials this year quite challenging compared to the one last year, which I finished on time apart from q11a (at home of course), so when I challenged my boi Sharky in getting 100 for the 2019 edition I was somewhat confident I could get rather close to that score (which turned out wasn't to be). I guess when I started the paper, q11 kinda already bombed out because q11a was written by none other than Sharky and Paradoxica (ended up not getting anything), and a combination of typos and my incompetence meant out of what should have been an easy 12 marks for q11, I only managed to convert 8 of them. However, apart from skipping a few 2-3 markers along the way throughout the rest of the exam which I felt would take too much time for the number of marks it was worth, the rest of the paper was somewhat manageable, if a little demanding on time.

For those people who are surprised about someone getting 80, I believe it's definitely possible for someone in the future to climb quite a bit higher into perhaps mid-85 range, and I don't expect the 80 record to stay for too long before someone eventually exceeds that score.

if you guys have any questions then you can post something below or send a message but I probably won't answer much because I'm a very irregular user of this website (and definitely don't mention about the test yesterday)

once again thanks to the people who made the BoS trials possible this year and I hope to possibly work with some of you in making an even harder 4u test next year.

bye

#### Trebla

When will we get our 3u results back?
Working on it. Usually aim for few days before the HSC exam.

#### sharky564

##### Member
WOW THAT IS SO COOL!!!

Is it true you were on the Australian olympiad team as well? What's harder, 4u or the international olympiad?
Everyone who's got experience in oly maths can confirm international maths olympiad is much harder than 4u maths.

4u maths - requires maybe a month or so to get good at
oly maths - years of training required, thousands of hours doing maths

#### blyatman

##### Well-Known Member
WOW THAT IS SO COOL!!!

Is it true you were on the Australian olympiad team as well? What's harder, 4u or the international olympiad?
lol if olympiad was easier than 4u then almost everyone who could cope with 4u would be on the team. It's a different type of focus - olympiad is about problem solving using topics like number theory, whereas 4u is mindlessly hashing out calculus.

#### blyatman

##### Well-Known Member
@sharky564 what's your plans for uni? I hope you're planning to study in the US or UK.

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#### realandbounded

##### New Member
Everyone who's got experience in oly maths can confirm international maths olympiad is much harder than 4u maths.

4u maths - requires maybe a month or so to get good at
oly maths - years of training required, thousands of hours doing maths
Wow were you on the Australian team too? Are all the people super maths geeks who do maths all the time?

#### sharky564

##### Member
Wow were you on the Australian team too? Are all the people super maths geeks who do maths all the time?
no, not quite, but close

also, if i did maths all the time, i'd probably bomb out in my atar, so we'll see

#### realandbounded

##### New Member
no, not quite, but close

also, if i did maths all the time, i'd probably bomb out in my atar, so we'll see
Come on Sharky...didn't the name give it away?

#### Arrowshaft

##### Well-Known Member
Wow, absolute legends BoS maths people. I wish I gave the BoS papers a go, they seem really fun!

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#### Lauralin24

##### New Member
When will we get our 3u results back?
HI,

I can tell you are very good at math. can you help? I need some 2018 mathematics extension 1 trial papers to practice. I can't find any except BoS.

If you have some, do you mind emailing me some at lauralin24@hotmail.com.

Thanks a lot. wish you get state rank for 3u and 4u math.

#### Trebla

Just a few remarks on the parametrics question after marking Q11 for the Mathematics Extension 1 paper:

In (b)(ii) far too many students derived the coordinates of P' (intersection of tangents at P and R) by deriving the equations of tangents at P and R and then finding their intersection. This was not necessary, as the coordinates can be deduced from T (intersection of tangents at P and Q).

In (b)(iii) many students made some assumptions trying to simplify

$\bg_white \dfrac{|q-r|+|p-r|}{|p-q|}$

either by ignoring the absolute values completely and fudging it, or only assuming one case (say p>q).

Students needed to carefully explain how to resolve the absolute values. Better responses showed that both cases p<r<q or q<r<p simplify the absolute values down to the same answer.

#### Trebla

Further feedback for students after marking Q12 of the Extension 1 paper.

• For the inverse trigonometric functions question, almost every student got the derivative of $\bg_white f(x)=\sin^{-1}(2x^2-1)$ incorrect. The most common mistake was asserting that
$\bg_white \dfrac{4x}{\sqrt{4x^2-4x^4}}=\dfrac{2}{\sqrt{1-x^2}}$

Firstly, you can only cancel out x for non-zero x values. Secondly, the square root of $\bg_white x^2$ is $\bg_white |x|$ not $\bg_white x$. Hence, the expression should actually simplify to:
$\bg_white \dfrac{4x}{\sqrt{4x^2-4x^4}}=\dfrac{2x}{|x|\sqrt{1-x^2}}$

By considering the positive and negative cases of x, you can then work out the correct derivative. The derivative is in fact undefined for x=0.

• Also on the inverse trigonometric function question, a lot of students sketched $\bg_white y=\sin^{-1}(2x^2-1)$ independently of what they incorrectly found for the derivative - which is good to see. The inconsistency between the sketch of the curve and the sketch of its derivative should prompt you to have a second thought about your answers.

However, a lot of students incorrectly showed two inflexion points in their sketch. Inflexion points occur where the derivative function has a stationary point. Full marks could not be awarded for having those two inflexion points for $\bg_white y=\sin^{-1}(2x^2-1)$ even for carry over errors because the (incorrect) sketch of $\bg_white y=f'(x)$ in part (ii) often did not show any stationary points for that same x-coordinate.

• On the SHM question, a common answer for the amplitude in part (ii) was $\bg_white v_0$. However, this assumes that $\bg_white v_0$ is positive. Better responses recognised that the amplitude of the curve $\bg_white y=A\cos x$ is not $\bg_white A$, but is in fact $\bg_white |A|$.

#### blyatman

##### Well-Known Member
The square root of $\bg_white x^2$ is $\bg_white |x|$ not $\bg_white x$
The number of times I have to drill that into my students... It pops up every few weeks, and no matter whether it's the 2u 3u or 4u class, it's always the same answers: x, or +-x.

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#### Trebla

...and here is the latest version of Mathematics Extension 1 paper, solutions (now with colour in the graphs!) and results.

And that's wrap so thanks to everyone who helped and participated this year!

To the students, best of luck for the Mathematics Extension 1 HSC exam!

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#### Drdusk

##### π
Moderator
...and here is the latest version of Mathematics Extension 1 paper, solutions (now with colour in the graphs!) and results.

And that's wrap so thanks to everyone who helped and participated this year!

To the students, best of luck for the Mathematics Extension 1 HSC exam!
Haha this guy broke all the bos trial records. Well done 3705, 67/70.