Edexcel C3,C4 June 2013 Thread

Can someone please help me with question 5c on the C3 june 05 paper.
I don't understand how they got Sin alpha = 4 and Cos alpha = 6 , wouldn't it be the other way around?

My motto is

"If you practiced and worked really hard, there is no reason why you shouldn't get full marks!!!"

PRACTISE, until you're in a state where you're looking forward in doing the exam. Nearly there guys.

Why are we having replacing papers for c4? Is it going to be harder?

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Am i the only guy finding it hard to break through the 69-72 barrier everytime those range questions or a stupid mistake like losing values in trig gets me should i just keep workin then see if i improve or is there any exam skills im lacking to iron out those extra marks 3-4 marks makes a big difference thats one of the bad things bout maths one silly mistake and you could drop 5ums 2 mistakes a grade so annoying

No, I only mean because you said year, rather than day or week .

For C4, they usually take me around 45 minutes if i'm doing it quickly. If I was doing one properly, checking for mistakes as I go along, it would probably take me around an hour or an hour and ten minutes. What I find really useful is to re answer some questions using a different method or to check it by substituting numbers in. e.g.

For partial fractions, try substituting in a number to see if you get the same answer as if you put it into the original expression. You could also try re expressing it as a single fraction afterwards.

For the binomial expansion questions, try putting in a number to see if you get anywhere close to what you get if you put it into the original expression.

For parametric questions, you could always try converting to Cartesian and doing the question again that way.

For integration questions, you could always see if you can find another method of doing it. Also, if you have a calculator that can do numerical integration, you could use that to check your integration by substituting in your own limits if none were given in the question. Just make sure you can actually do it yourself though .

Just doing things like this will help you reduce a lot of the silly mistakes that you can make.

However, only do these if you finish the other questions early!!

For the trig questions, once again, substituting in your values will tell you whether they work or not.

For iterations (and some other questions), if you have the fx-991es, you can actually type in the equation you want to solve and it may give you the solution. If not, then the rest of the question usually acts as a check anyway.

For differentiation, once again I substitute a number in and then check it on my calculator using the numerical differentiation option.

For my C3 exam, my teacher let me borrow a graphics calculator. So what I did for one of the questions (it was the trig fraction one in the C3 jan 2013 paper) is sketch the graph on the calculator and then find the maximum turning point on the calculator to see if that value of theta was the same as the one I calculated. So drawing some of the graphs can be a really good check for some questions as well.

As with partial fractions, for the 'express as a single fraction in its simplest form questions', substituting in numbers is enough for that.

I wouldn't necessarily, finish all the papers by a certain time. I would just keep doing them until your exam, but not with the aim of finishing them all as quickly as possible but rather to make sure you properly understand and can answer all the questions in the papers.

The awkward moment when they create a Paper which is 10x harder.....

Lol tbh we will see if i "destroy" FP3 like i will to FP2 and C4
I just got the pack of all the c3 questions someone put up on here and just been going through them, no point marking it as i remember most of the questions lol.
I just did a C4 paper, june 2012, gt 74/75 lol I think it's because i double checked literally everything which i don't tend to do for maths past papers hence why not full marks lol. I lost the one mark because i forgot when you 4th root something, you get two values .
Tbh that paper was nice, i haven't found a single hard C4 paper :/ some vector questions are hard though, and as i kind have forgotten some of my gcse shape formulas u err lose marks there lol.
My confidence is this.....YOLO lol.
Erm STEP is going fine tbh, i'm on 2005 paper, nearly done the pure questions and going to do the mechanics question..no stats questions ,, and start 2006. But STEP II, i will flop! 100% :P
Lol you want me to get into warwick because you can say your mum, look an asian guy from east london who is considered a chav got it lol
You're an amazing weird asain lol.
Btw did you know there's this one person who's also doing STEP, he can do a question in 10 mins without even thinking that much o.O

I'd be surprised if they got either, since they both have to be < or = to 1.

i.e. put the R in or what you're writing is nonsense and will be penalised.

Why did everyone thumbs down Tiny Hobbit

She's a Teacher here to help! Show her some respect hahaha

She was a LIFESAVER in the D1 thread. My Teacher didn't help much at all!!

on questions like this, (part a) for the value of alpha you either do tan-1 5/3 or tan-1 3/5, but for some reason it varies depending on how the question is laid out - i don't understand why. I'd normally assume you just do the number before sin over the number before cos but it doesn't always give the correct answer.

Does anyone understand what I mean? Can anyone explain to me how to know what way to do it?

I'll try give you a step by step of how I think it should be done.

1. If it says in the form, Rcos(x+a), expand this. Then it becomes: Rcosxcosa - Rsinxsina.

2. Equate your expansion to the expression given. Rcosxcosa - Rsinxsina = 5cosx - 3sinx.

3. At this point, you want to equate coefficients. You want to equate the terms with cosx in them, and with sinx. From this, you can see, Rcosxcosa = 5cosx. Rsinxsina = 3sinx.

4. Simplify. Rcosa = 5. Rsina = 3. All I have done is cancelled cosx and sinx from the expressions.

5. To get Tan(a), you do Rsina / Rcosa, as this cancels the R terms, and sin/cos = tan.

Therefore, Tan(a) = 3/5.

Sorry if this is a bit hard to read, I can't do that fancy formatting stuff, but shout if you need more help.

I'll try give you a step by step of how I think it should be done.

1. If it says in the form, Rcos(x+a), expand this. Then it becomes: Rcosxcosa - Rsinxsina.

2. Equate your expansion to the expression given. Rcosxcosa - Rsinxsina = 5cosx - 3sinx.

3. At this point, you want to equate coefficients. You want to equate the terms with cosx in them, and with sinx. From this, you can see, Rcosxcosa = 5cosx. Rsinxsina = 3sinx.

4. Simplify. Rcosa = 5. Rsina = 3. All I have done is cancelled cosx and sinx from the expressions.

5. To get Tan(a), you do Rsina / Rcosa, as this cancels the R terms, and sin/cos = tan.

Therefore, Tan(a) = 3/5.

Sorry if this is a bit hard to read, I can't do that fancy formatting stuff, but shout if you need more help.

thank you! this made perfect sense
i always just guessed these questions because i got it right half the time which is stupid

Hey, I was wondering why alpha would not be = tan ^-1( -3/5) ...

The formula I use is alpha = tan^-1 (B/A)

Do you not take into account the sign of the number?

You're not the only one don't worry, you're welcome



The reason is that if you look at the equating coefficients part, I have equated Rsinxsina = 3sinx. If you took into account negatives then they would cancel, because the original expansion actually has a term -Rsinxsina. If you say, -Rsinxsina = -3sinx, then the negatives just cancel. I didn't equate them by including the negatives, but they'll cancel every time anyway.

So the sign does not make a difference, because the sign on the term, and the sign on the expansion will both cancel.

Thank you for the explanation I understand it better now!

So can I always just use the positive value of B and A and plug them into the formula alpha = Tan^-1 (B/A) and get an answer? Or should I double check with the method you just showed?