Maths Ext 2 Predictions/Thoughts (6 Viewers)

notme123 · Nov 16, 2021

Trebla said:
Well for starters it can’t be right as that is beyond the range for a sine function. The errors seems to be where you squared the constant term in your discriminant...

omg im an idiot thank you hahaha

notme123 · Nov 16, 2021

new solution

$r.v=0$
$u^2t\cos{\theta}^2+(u\sin{\theta}-gt)(ut\sin{\theta}-\frac{1}{2}gt^2)=0$
dividing everything by t and simplifying:
$2u^2 -3u\sin{\theta}gt+g^2 t^2=0$
$\Delta >0$
$(-3gu\sin{\theta})^2-4{g}^2(2u)>0$
$\sin{\theta}^2>\frac{8}{9}$
$\therefore 1>\sin{\theta}>\frac{2\sqrt{2}}{3}$
$\therefore \frac{\pi}{2}>\theta>\arcsin{\frac{2\sqrt{2}}{3}}$
or $\therefore \frac{\pi}{2}>\theta>\arccos{\frac{1}{3}$

is this correct or are there specific values for theta in this range

tito981 · Nov 16, 2021

notme123 said:
new solution

$r.v=0$
$u^2t\cos{\theta}^2+(u\sin{\theta}-gt)(ut\sin{\theta}-\frac{1}{2}gt^2)=0$
dividing everything by t and simplifying:
$2u^2 -3u\sin{\theta}gt+g^2 t^2=0$
$\Delta >0$
$(-3gu\sin{\theta})^2-4{g}^2(2u)>0$
$\sin{\theta}^2>\frac{8}{9}$
$\therefore 1>\sin{\theta}>\frac{2\sqrt{2}}{3}$
$\therefore \frac{\pi}{2}>\theta>\arcsin{\frac{2\sqrt{2}}{3}}$

is this correct or are there specific values for theta in this range

that should be right

notme123 · Nov 16, 2021

tito981 said:
that should be right

if it is im mad rn because i did this exact same thing in the exam i just messed up the expanding and simplification cuz of algebraic mistakes. how many marks would i get?

also how does one explain the justification part

Trebla · Nov 16, 2021

For completeness you should ideally also justify that the two points are on the projectile itself (i.e. not on the part of the parabolic equation where y < 0)

Paradoxica · Nov 16, 2021

look at the sum and product of roots of the quadratic to show that they are both positive

Siwel · Nov 16, 2021

notme123 said:
new solution

$r.v=0$
$u^2t\cos{\theta}^2+(u\sin{\theta}-gt)(ut\sin{\theta}-\frac{1}{2}gt^2)=0$
dividing everything by t and simplifying:
$2u^2 -3u\sin{\theta}gt+g^2 t^2=0$
$\Delta >0$
$(-3gu\sin{\theta})^2-4{g}^2(2u)>0$
$\sin{\theta}^2>\frac{8}{9}$
$\therefore 1>\sin{\theta}>\frac{2\sqrt{2}}{3}$
$\therefore \frac{\pi}{2}>\theta>\arcsin{\frac{2\sqrt{2}}{3}}$
or $\therefore \frac{\pi}{2}>\theta>\arccos{\frac{1}{3}$

is this correct or are there specific values for theta in this range

i thought the question said there are 2 theta values you need to find not a range

dbramley · Nov 16, 2021

Siwel said:
i thought the question said there are 2 theta values you need to find not a range

Two times didn't give a restriction on theta

Siwel · Nov 16, 2021

dbramley said:
View attachment 33789
Two times didn't give a restriction on theta

hm fair enough i just solved for theta values but believe had the same a similar eq at some point then everything like the u's, g's etc cancelled and i got theta =0 and some other exact value

Grinder · Nov 16, 2021

Hello Everyone, I am currently doing maths ext 2, will be having my HSC in 2022, any advice for me to keep in mind along the year. I do go to a school ranked in the 100s.

ohnose · Nov 16, 2021

Grinder said:
Hello Everyone, I am currently doing maths ext 2, will be having my HSC in 2022, any advice for me to keep in mind along the year. I do go to a school ranked in the 100s.

Work hard, think about concepts deeply and most of all...

Enjoy it! Extension 2 Maths is a rewarding journey for those who put effort in, irrespective of what your final mark is.

icycledough · Nov 16, 2021

Grinder said:
Hello Everyone, I am currently doing maths ext 2, will be having my HSC in 2022, any advice for me to keep in mind along the year. I do go to a school ranked in the 100s.

It will most likely take up the most time of your subjects (and should rightly so as it will comprise of 40% of your entire HSC). It is definitely rewarding with its alignment in the HSC, but that doesn't mean you should RELY on it. As said above, put in the hard work (a consistent grind), even if it is just 1/2 to an hour every day (past exams, questions, homework, etc) and let the scaling do its 'magic' for you. Youtube videos are a great source (sometimes not given enough credit by people), especially people like Eddie Woo, who explains many maths topics in such great depth and very concisely. It will be challenging, but stay perseverant and you will be able to reap the benefits from it.

Eagle Mum · Nov 16, 2021

CM_Tutor said:
You are correct, so that means there should be open circles at $z = -\pi$ and at $z=0$ and the boundary along the real axis between them should be dotted.

Good catch!

DS did actually realise both of these properties which made him think the region was much more complicated than it turned out to be, so time ran out before he started on the proper graph. He has a lot of rough workings & sketches, but no idea whether they'll count for much. Overall, he thought it was a good paper which explored mathematical concepts to more depth than previous years, but he is fortunate in having the luxury of sitting next year's paper if he's not happy with his final mark.

notme123 · Nov 16, 2021

Eagle Mum said:
DS did actually realise both of these properties which made him think the region was much more complicated than it turned out to be, so time ran out before he started on the proper graph. He has a lot of rough workings & sketches, but no idea whether they'll count for much. Overall, he thought it was a good paper which explored mathematical concepts to more depth than previous years, but he is fortunate in having the luxury of sitting next year's paper if he's not happy with his final mark.

who is ds, are they accelerated?

dbramley · Nov 16, 2021

Eagle Mum said:
DS did actually realise both of these properties which made him think the region was much more complicated than it turned out to be, so time ran out before he started on the proper graph. He has a lot of rough workings & sketches, but no idea whether they'll count for much. Overall, he thought it was a good paper which explored mathematical concepts to more depth than previous years, but he is fortunate in having the luxury of sitting next year's paper if he's not happy with his final mark.

Luxury yes and no

Eagle Mum · Nov 16, 2021

notme123 said:
who is ds, are they accelerated?

My ‘dear son‘ who is in Yr 11 & only accelerated in maths.

notme123 · Nov 16, 2021

Eagle Mum said:
My ‘dear son‘ who is in Yr 11 & only accelerated in maths.

wow he must be bright if he wasn't at the least slightly perturbed by the exam

icycledough · Nov 16, 2021

I only thought there were certain subjects you could accelerate in Year 11 (like Modern History, IPT, Business Studies, etc). I've heard of 4U students accelerating 2U in Year 11 (which obviously won't count for their HSC but can help the current Year 12 current), but never people accelerating 4U and 3U. When would they learn the Year 11 content?

dbramley · Nov 16, 2021

icycledough said:
I only thought there were certain subjects you could accelerate in Year 11 (like Modern History, IPT, Business Studies, etc). I've heard of 4U students accelerating 2U in Year 11 (which obviously won't count for their HSC but can help the current Year 12 current), but never people accelerating 4U and 3U. When would they learn the Year 11 content?

It’s offered at certain schools depending on the child a lot of the time. You don’t “miss out” on the year 11 content you just start it a year earlier with the cohort above so in effect skipping the year 10 syllabus content.

ExtremelyBoredUser · Nov 16, 2021

Would they have to do accel 3u alongside accel 4u?

Maths Ext 2 Predictions/Thoughts (6 Viewers)

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