Mathematics Question Thread

[jamonwindeyer]

Hey!
How can I differentiate this?

Oh this is cool! Do this:



You can then tackle that with the quotient rule! Let me know if you need a hand with it, but you should get:



Or some factorised form of it

[K9810]

Oh this is cool! Do this:



You can then tackle that with the quotient rule! Let me know if you need a hand with it, but you should get:



Or some factorised form of it

Thanks for helping!

[1937jk]

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Okay cool thank you! I understand now !

[1937jk]

hey,
so just trying to integrate tanx so sinx/cosx but I'm confused and don't understand how to do it

[RuiAce]

hey,
so just trying to integrate tanx so sinx/cosx but I'm confused and don't understand how to do it

[Fahim486]

Hey so I can't figure out how to do question 9. iii) and the answer says it's 7-3ln7 and I don't know how they figured it out. Thanks

[RuiAce]

Hey so I can't figure out how to do question 9. iii) and the answer says it's 7-3ln7 and I don't know how they figured it out. Thanks

Reading off your sketch, the maximum clearly occurs at the endpoint at x=7. So upon substituting in x=7 we have y=7-3ln7

[Thebarman]

Hey guys, I'm working through a past paper right now and I'm slightly stuck on the second part of a question. I'm trying to simplify 15pi/2 - 9/2 sin(5pi/3). It needs to be in exact form, and I'm not sure how to simplify sin 5pi/3. According to the answers, that particular part simplifies to -root3/2. How do I get to this?
I've attached the question in case my message is a bit confusing.

Thank you!

EDIT:

As far as the HSC goes, the only way to sketch that is to first sketch y=3cos(x) and y=-cos(2x) separately (AND to scale), and then add the y-coordinates together. This is essentially how superposition of waves work.

My honest opinion - it's such an annoying process.

If you want to find the intercepts of 3cos(x) and cos(2x), upon equating you get 3cos(x) - cos(2x) = 0 so you just look at where all your x-intercepts are.

Thanks for the reply! I definitely agree that it's an annoying process. Do you mind clarifying what you mean about looking at where all the x-intercepts are? Thanks again

[RuiAce]

Hey guys, I'm working through a past paper right now and I'm slightly stuck on the second part of a question. I'm trying to simplify 15pi/2 - 9/2 sin(5pi/3). It needs to be in exact form, and I'm not sure how to simplify sin 5pi/3. According to the answers, that particular part simplifies to -root3/2. How do I get to this?
I've attached the question in case my message is a bit confusing.

Thank you!

EDIT:
Thanks for the reply! I definitely agree that it's an annoying process. Do you mind clarifying what you mean about looking at where all the x-intercepts are? Thanks again

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That statement was mildly dependent on what you're intersecting. I took a guess as to what you were trying to intersect but I never knew what you meant, so perhaps ignore what I said and maybe make your question clearer for me please?

[Thebarman]

Thanks for the answer, that's exactly what I was asking about. I had misread the exact ratios and gotten them jumbled up, which is why I couldn't get the answer

[12070]

Hey guys,

So I have a question on the mark allocation on one of my questions in a test.

The question states 'John has borrowed $200,000. The interest rate is 6% p.a compounded monthly.'
iii.) If John pays $10,000 to the loan each month, find how long it will take him to reduce the loan to $100,000.

I know how to do the question but just made a calculation error saying that 10,000/0.005 was 200,000 instead of 2 million.
My answer is attached; which I can re-write if you can't read it but my teacher wasn't giving me any marks for it which I'm a little surprised about so would love to hear your thoughts.

[Wales]

Hey guys,

So I have a question on the mark allocation on one of my questions in a test.

The question states 'John has borrowed $200,000. The interest rate is 6% p.a compounded monthly.'
iii.) If John pays $10,000 to the loan each month, find how long it will take him to reduce the loan to $100,000.

I know how to do the question but just made a calculation error saying that 10,000/0.005 was 200,000 instead of 2 million.
My answer is attached; which I can re-write if you can't read it but my teacher wasn't giving me any marks for it which I'm a little surprised about so would love to hear your thoughts.

How many marks was the question? Do you have the question paper? If it was 3 marks or so I would be curious as to why you did not receive at least 1 for carry on. At least that's what I've been told. Correct me if I am wrong.

[12070]

How many marks was the question? Do you have the question paper? If it was 3 marks or so I would be curious as to why you did not receive at least 1 for carry on. At least that's what I've been told. Correct me if I am wrong.

Yeah; it was worth 3 and I'm really gutted about it because I know how to do it and I got the same mark as someone who didn't even atempt the question.Normally I wouldn't mind too much but the test was worth 35% (because our mid-course got due to flooding in Lismore) and only out of 42 so that's almost a percent for every mark. Anyway, do you know how I should argue on Monday because if I had made a similar mistake towards the end i know for a fact that I would get 2 arks but because it was so early I got 0. Don't really understand it to be honest.

[Wales]

Yeah; it was worth 3 and I'm really gutted about it because I know how to do it and I got the same mark as someone who didn't even atempt the question.Normally I wouldn't mind too much but the test was worth 35% (because our mid-course got due to flooding in Lismore) and only out of 42 so that's almost a percent for every mark. Anyway, do you know how I should argue on Monday because if I had made a similar mistake towards the end i know for a fact that I would get 2 arks but because it was so early I got 0. Don't really understand it to be honest.

It does seem like you skipped multiple steps there, your teacher left 2 question marks. I've seen teachers mark people down for not showing working. My advice would be to ask the teacher and ask where the marks where allocated and check it over with what you've done.

I assume the mark allocation to be
1 for finding the equation 100000=200000x1.005^n-10000(1.005^n-1/0.005)  (nope)
2 for reorganising for n (carry on? but you skipped like 3 lines of working)
3rd for the answer? (nope)

But I can't be sure. You've skipped far too many steps there. See what Rui says.

[jamonwindeyer]

I absolutely agree with Wales! Assuming it is otherwise perfectly correct (which I think it is, at a guess) you should absolutely get marks for method, but it looks like you've skipped a fair few steps (this is why working is important, if you get the answer wrong, the working is where your marks come from!)

Definitely worth following up - I'd wager you could get a single mark for what you did show