VCE Methods Question Thread!

[keltingmeith]

how to approach questions where it says things like f(u)f(v) = f(u) + f(v) - f(u+v)? I usually sub u and v in and make it equal to each other and the calc says its true but that doesn't show anything.

Just... Do that, really. Granted, off the top of my head, I can't think of a function that works like this...

Personally, I never trusted my calc for some reason on those questions, so I always did it by hand. I got pretty fast at it, but this late in the game, you might be better off going with the calc and hope it only says true for one of the options.

[IndefatigableLover]

Aha, I replied soon after;

I see where you are coming from but I'm still not sure to why we halve 8/3. I understand he has to make a smooth trip without any interruptions but why would this cause 8/3 to be divided by 2?

Haha whoops I didn't see that LOL
And well 8/3 is the total time he can actually try and get to the diamond and back but this is at two separate times (indicated by the graph at 2b when you draw a line at 1250 since in between the two min points there's a max in between). You divide the total time by two, then you get the time for one of those periods which he can go get the diamond.

Think of it like this, how did you calculate your answer to Q2 e)? Did you split it up into two times to get 8/3? It's pretty much just choosing just one of them and using that value as your answer (since whatever one you chose would have given you 4/3 as your answer).. I know my explanation is a bit hard to follow so sorry if you couldn't follow that :/

[vcestudent123]

Could somebody please explain Question 9b on the 2010 Math Exam 1.

[Jason12]

the report says the terminals for 5b are 30 and 25 but I don't get why. I thought it was 25 and 20

[Equilibriaas]

Could it be due to symmetry? They are same? Not sure sorry.

[IndefatigableLover]

(Image removed from quote.)

the report says the terminals for 5b are 30 and 25 but I don't get why. I thought it was 25 and 20

Well the terminals are 30 and 25 since they've subtracted it from '1'. When you draw the graph out, and draw a line at t=25, you're looking for the area between t=10 and t=25 (since it wants to complete the full circuit in less than 25 minutes). What they did was find the area between t=25 and t=30 and subtracted it from 1 since it'll give the same answer!

So you could have also use the terminal the terminals as 25 and 10 for f(t)

[Robert123]

Could somebody please explain Question 9b on the 2010 Math Exam 1.

Hint, use your results from part a and approach it like it is an integration by recognition type question.
Try that and tell me if you have any more problems 

[Reus]

Someone  know how to do Q6b exam 1 2012? Thanks!

[Valyria]

Haha whoops I didn't see that LOL
And well 8/3 is the total time he can actually try and get to the diamond and back but this is at two separate times (indicated by the graph at 2b when you draw a line at 1250 since in between the two min points there's a max in between). You divide the total time by two, then you get the time for one of those periods which he can go get the diamond.

Think of it like this, how did you calculate your answer to Q2 e)? Did you split it up into two times to get 8/3? It's pretty much just choosing just one of them and using that value as your answer (since whatever one you chose would have given you 4/3 as your answer).. I know my explanation is a bit hard to follow so sorry if you couldn't follow that :/

Ffs, so he went in as soon as the concentration was first below 1200. Were we just meant to assume he didn't go in at t=0 when the concentration was deemed 'deadly'?

Explanation was quality, thanks mate

[Blondie21]

Ffs, so he went in as soon as the concentration was first below 1200. Were we just meant to assume he didn't go in at t=0 when the concentration was deemed 'deadly'?

Explanation was quality, thanks mate

Haha why would Tasmania go in when the concentration was deadly :p

[AbominableMowman]

Someone  know how to do Q6b exam 1 2012? Thanks!

Yeah
So you know that tan(pi/3)=sqrt(3) from part a, because x=pi/3 is the intersection of the graph at the first point
For the second point, you need to follow the unit circle and figure out at which point tan(x) is equal to sqrt(3) again, which is at 4pi/3 in quadrant 3.

[Robert123]

Someone  know how to do Q6b exam 1 2012? Thanks!

Cos(x)=sin(x)/sqrt(3)
(Multiple both sides by sqrt(3)/cos(x(
Sqrt(3)=sinx/cosx (oh look, that is the definition of the tan function  )
tanx=sqrt(3)

Well you should be able to do the rest from there easily

[vcestudent123]

Hint, use your results from part a and approach it like it is an integration by recognition type question.
Try that and tell me if you have any more problems 

Luckily I asked about it because I completely forgot about integration by recognition...

Thanks

[AbominableMowman]

Haha why would Tasmania go in when the concentration was deadly :p

Because Tasmania is actually just a methods teacher who wants to make all the students' lives hell. Simple answer

[Valyria]

Haha why would Tasmania go in when the concentration was deadly :p

I suppose I just wanted him to face a deadly concentration of insects