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Year 13 Maths Help Thread

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Thanks again.
Original post by Palette
(special mention to Zacken for putting up with my silly C3/C4 inquiries!).


Original post by Palette
with credit due to the helpers (especially Zacken) for making this project work!


Woot! Thanks for the special mention! Great thread, props to you. I'd like to have a special shout out to @SeanFM for his invaluable help here and elsewhere.
To those going on to A2 maths... please, please don't ever underestimate the subject! It doesn't matter if you're breezing through gold papers, maths is completely unpredictable. At the same time, don't give up if you find you're just spinning your wheels. Your maths skill over the next year will be like an exponential curve; you'll surely get the hang of it around February-April :smile:

Maths alone needs to be the majority of your revision. There's hardly any memory involved in maths aside from remembering previous past paper questions. It's all practice. There's a saying; the more I prepare, the luckier I get. During study leave, your revision has to increase in intensity right up to the exam day, and you cannot afford to leave gaps in the year where you haven't practiced maths papers. Your ability will falter.

I am by no means a good mathematician. This is just advice from a wounded survivor. Good luck, and appreciate the unique challenge the subject gives you. I'll always be envious of those gifted in mathematics.
(edited 7 years ago)
Original post by hopefuldentist10
To those going on to A2 maths... please, please don't ever underestimate the subject! It doesn't matter if you're breezing through gold papers, maths is completely unpredictable. At the same time, don't give up if you find you're just spinning your wheels. Your maths skill over the next year will be like an exponential curve; you'll surely get the hang of it around February-April :smile:

Maths alone needs to be the majority of your revision. There's hardly any memory involved in maths aside from remembering previous past paper questions. It's all practice. There's a saying; the more I prepare, the luckier I get. During study leave, your revision has to increase in intensity right up to the exam day, and you cannot afford to leave gaps in the year where you haven't practiced maths papers. Your ability will falter.

I am by no means a good mathematician. This is just advice from a wounded survivor. Good luck, and appreciate the unique challenge the subject gives you. I'll always be envious of those gifted in mathematics.


Thanks for your advice, I appreciate it. Unlike last year, this time i will listen to older students and start revising early!! :biggrin:
Original post by RDKGames
Congratulations! Don't worry, A2's will be a breeze if you keep it up. :congrats:


Thank you!! Haha hopefully :biggrin:
Original post by Zacken
Woot! Thanks for the special mention! Great thread, props to you. I'd like to have a special shout out to @SeanFM for his invaluable help here and elsewhere.


A moment of silence for some disappointed Warwick Admissions Tutors. And a well done.
Original post by SeanFM
A moment of silence for some disappointed Warwick Admissions Tutors. And a well done.


Thank you very much!
Reply 407
I spent age doing a relatively simple trigonometry question as I mislabelled 6cosθ6\cos \theta and 6sinθ6\sin \theta because I drew the right angled triangle weirdly. Shows how important drawing a good diagram is.
Original post by Palette
I spent age doing a relatively simple trigonometry question as I mislabelled 6cosθ6\cos \theta and 6sinθ6\sin \theta because I drew the right angled triangle weirdly. Shows how important drawing a good diagram is.


Just label theta onto the other angle and you're good, if you mixed up the sides with those labels :tongue:

(pls tell me you didn't label the hypotenuse as one of those... :facepalm:)
I've been to Edexcel's page for the AEA award. The page is poorly set and there is no information of when the next tests are to be sat(or previous dates). I just finished learning the C3 and C4 , I know that the paper tests/advances skills in C1-C4. Do you have to pay to sit the paper like you do for STEP. Around what time of the year are the papers sat?
Reply 410
Original post by RDKGames
Just label theta onto the other angle and you're good, if you mixed up the sides with those labels :tongue:

(pls tell me you didn't label the hypotenuse as one of those... :facepalm:)


The hypotenuse was 6; I just wrote 6cosθ6\cos \theta where I was supposed to have written 6sinθ6\sin\theta and vice versa. It was a Madas C2 paper, which was interesting (some questions were of normal difficulty while others were truly fiendish).
Original post by Palette
The hypotenuse was 6; I just wrote 6cosθ6\cos \theta where I was supposed to have written 6sinθ6\sin\theta and vice versa. It was a Madas C2 paper, which was interesting (some questions were of normal difficulty while others were truly fiendish).


Yeah just label the other angle as theta instead then rather than cross out the side lengths haha. Link the paper? I'm bored :smile:
Original post by Dynamic_Vicz
I've been to Edexcel's page for the AEA award. The page is poorly set and there is no information of when the next tests are to be sat(or previous dates). I just finished learning the C3 and C4 , I know that the paper tests/advances skills in C1-C4. Do you have to pay to sit the paper like you do for STEP. Around what time of the year are the papers sat?


Yes, you need to pay. You need to sit them in June.
Reply 413
Original post by RDKGames
Yeah just label the other angle as theta instead then rather than cross out the side lengths haha. Link the paper? I'm bored :smile:


http://madasmaths.com/archive/iygb_practice_papers/c2_practice_papers/c2_t.pdf

Q5, rather simple as long as you draw a good diagram.
Reply 414
1) f(x)=(x23x)/(x+1) f(x)= (x^{2}-3x) / (x+1)
I worked out f '(x) as (x2+2x3)/(x+1)2 (x^{2}+2x-3) / (x+1)^{2}
I'm stuck on how to work out the values of x for which f(x) is decreasing.

2) Differentiate x / x+1\sqrt {x+1}
I rearranged it to x(x+1)1/2 x(x+1)^{-1/2} and differentiated it as x/2(x+1)3/2 -x / 2(x+1)^{3/2}
The book's answer is x+2/2(x+1)3/2 x+2 / 2(x+1)^{3/2}
Original post by osayukiigbinoba
1) f(x)=(x23x)/(x+1) f(x)= (x^{2}-3x) / (x+1)
I worked out f '(x) as (x2+2x3)/(x+1)2 (x^{2}+2x-3) / (x+1)^{2}
I'm stuck on how to work out the values of x for which f(x) is decreasing.

2) Differentiate x / x+1\sqrt {x+1}
I rearranged it to x(x+1)1/2 x(x+1)^{-1/2} and differentiated it as x/2(x+1)3/2 -x / 2(x+1)^{3/2}
The book's answer is x+2/2(x+1)3/2 x+2 / 2(x+1)^{3/2}


1. What is the definition of a decreasing function?

2. This one is icky as there's a lot of rearranging going on but the book is definitely right. Please show your working
(edited 7 years ago)
Reply 416
Original post by SeanFM
1. What is the definition of a decreasing function?

2. This one is icky as there's a lot of rearranging going on but the book is definitely right. Please show your working

Thank you for replying.
1. A decreasing function is when dy/dx < 0
2. x(x+1)^-1/2
Then I used the rule (ax+b)^n =an(ax+b)^n-1 because I couldn't get the right answer with the quotient rule either
dy/dx=1/2x(x+1)3/2dy/dx = -1/2x(x+1)^{3/2}
= x/2(x+1)3/2 -x/ 2(x+1)^{3/2}
Original post by osayukiigbinoba
Thank you for replying.
1. A decreasing function is when dy/dx < 0
2. x(x+1)^-1/2
Then I used the rule (ax+b)^n =an(ax+b)^n-1 because I couldn't get the right answer with the quotient rule either
dy/dx=1/2x(x+1)3/2dy/dx = -1/2x(x+1)^{3/2}
= x/2(x+1)3/2 -x/ 2(x+1)^{3/2}


So that should help you with question 1 :h:

You can't do that when you have two functions multiplied by eachother (in this case x and (x+1)^(-1/2). You can use the product rule or the quotient rule.
Reply 418
Original post by SeanFM
So that should help you with question 1 :h:

You can't do that when you have two functions multiplied by eachother (in this case x and (x+1)^(-1/2). You can use the product rule or the quotient rule.


I tried using the quotient rule but I'm not sure how to simplify this
(x+1)1/21/2(x+1)1/2(x)/(x+1) (x+1)^{1/2} - 1/2(x+1)^{-1/2}(x) / (x+1)
Original post by osayukiigbinoba
I tried using the quotient rule but I'm not sure how to simplify this
(x+1)1/21/2(x+1)1/2(x)/(x+1) (x+1)^{1/2} - 1/2(x+1)^{-1/2}(x) / (x+1)


Brilliant, so you've applied the rule correctly - it's the most tricky part, the simplifying, that you just need to do.

It's difficult to know what you want the simplified version to look like, but ideally you want no fractional powers in the numerator (after combining the two fractions) so you can multiply by the most appropriate numbers (eg if you had (x+1)^(1/2) and (x+1)^(-1/2) in the numerator then it would make sense to multiply both by (x+1)^(1/2) (this gets rid of both fractional powers) and move the thing you multiplied to the denominator.

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