Carrotsticks' MX2 HSC 2013 Solutions (2 Viewers)

[anomalousdecay]

The cut off for band 6 when the marking was out of 120 was 76ish. So a 68 should definitely net you a band 6.

But still the format is different now....

 

[Carrotsticks]

I just realised I totally missed Q11 (e).

 

[Carrotsticks]

Added it now =)

 

[anomalousdecay]

Who wants to join my "lost more marks in question 11 than in question 16" crew?

Spewin' really

Damn. Unlucky. That's why I spent 40 minutes on 11 and 12, and I think I only dropped 1 mark. Brain-freezed on the pendulum, the induction and the two geo questions though. I feel so dumb that I stuffed up the induction. It looks so simple now.

 

[anomalousdecay]

Carrot. The induction question asks for n greater than 2, not n=2.

Can you still use n=2 as a base case though? I tried to prove it for n=3 and failed.

 

[Carrotsticks]

Carrot. The induction question asks for n greater than 2, not n=2.

Can you still use n=2 as a base case though? I tried to prove it for n=3 and failed.

But the induction is for >

 

[seanieg89]

I made a triangle using the perpendicular bisector of CD, the radius OD, and half of CD. Then just a bit of trig.

I'm curious what was your approach?

Draw lines from O (centre of circle) to D,E,C. These form two angles a and b. We have sin(a/2), sin(b/2) and sin((a+b)/2) in terms of r since we know the triangle's side lengths. Then we can use the sine addition formula to give us an equation with only variable r, which is easy to solve.

Not particularly efficient but was the first thing that popped into my head.

 

[superSAIyan2]

i have a few questions regarding marking:

- for 13c)ii) i showed the result AE = 2rcosa sinB using the identity sin(a+b) = ... but i didnt see that we had to prove it in the next question. So will i lose 1 or 2marks?

- also for 15c)ii) i didnt read the question properly and thought there were 4 cars instead of 8. So my probability expression was similar to what RealiseNothing posted expect for 4 cars. Will this cost 1 or 2marks?

 

[hayabusaboston]

Carrot THANKYOU for your hard work, ive calculated ~70 raw for my mark, hope thats E4 :/

 

[Carrotsticks]

i have a few questions regarding marking:

- for 13c)ii) i showed the result AE = 2rcosa sinB using the identity sin(a+b) = ... but i didnt see that we had to prove it in the next question. So will i lose 1 or 2marks?

- also for 15c)ii) i didnt read the question properly and thought there were 4 cars instead of 8. So my probability expression was similar to what RealiseNothing posted expect for 4 cars. Will this cost 1 or 2marks?

Why do you need to prove AE=... again for the next question?

For 15, most likely -1 mark assuming everything else is correct.

 

[anomalousdecay]

i have a few questions regarding marking:

- for 13c)ii) i showed the result AE = 2rcosa sinB using the identity sin(a+b) = ... but i didnt see that we had to prove it in the next question. So will i lose 1 or 2marks?

- also for 15c)ii) i didnt read the question properly and thought there were 4 cars instead of 8. So my probability expression was similar to what RealiseNothing posted expect for 4 cars. Will this cost 1 or 2marks?

Same. I assumed it was 4 cars for some reason. We will indefinitely lose two marks.

 

[study1234]

For question 14 d) iv), would you lose marks for not simplifying the surd and rationalising the denominator?

 

[Web Addict]

I feel like shit after seeing how many silly mistakes I made.

 

[anomalousdecay]

But the induction is for >

Oops. You're right.

 

[harryharper]

For the radius question, I proved and used the 'extended' Sine Rule : a/sina = b/sinb = c/sin c = 2R. Works like a dream.

 

[iBibah]

I wonder how Fus ro dah went.

 

[Carrotsticks]

Same. I assumed it was 4 cars for some reason. We will indefinitely lose two marks.

I'm not going to lie, I first thought this too when I did the question.

For question 14 d) iv), would you lose marks for not simplifying the surd and rationalising the denominator?

Nope.

 

[knxd]

This is essentially a first draft so please let me know if there's a mistake somewhere.

https://www.dropbox.com/s/ao9yfa5reav9gq7/HSC 2013 Solutions.pdf

wow

 

[Fus Ro Dah]

Looking at solutions, I think I dropped 1 mark overall, in Question 13 (a) (ii). I used the formula for half of a circle instead of a quarter circle =(

 

[superSAIyan2]

Why do you need to prove AE=... again for the next question?

what i meant was that for c)ii) didnt know how to show AE=.... using triangle ABD. so instead i used a different method where i had to expand sin(a+b). only afterwards did i realise that the next question c) iii) asked us to 'hence show sin(a+b) =sinacosb + sinbcosa.'

So i was wondering how many marks i would lose for using that trig identity.