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# Edexcel A2 C4 Mathematics June 2016 - Official Thread watch

1. (Original post by ryanroks1)
Does anyone have an understandable proof for the integral of 2^x being (2^x)/ln2? Is it something we need to be able to prove?
Just use derivative of 2^x

2^x = e^(log(2^x)) = e^(xlog2)
Therefore derivative is log2e^(xlog2) = log2e^(log(2^x)) = log2(2^x)

hence the derivative of (2^x)/log2 is just log2(2^x)/log2 = 2^x

(note I mean the natural logarithm by log)
2. (Original post by 13 1 20 8 42)
Just use derivative of 2^x

2^x = e^(log(2^x)) = e^(xlog2)
Therefore derivative is log2e^(xlog2) = log2e^(log(2^x)) = log2(2^x)

hence the derivative of (2^x)/log2 is just log2(2^x)/log2 = 2^x

(note I mean the natural logarithm by log)
Great! Thank you
3. (Original post by ryanroks1)
Does anyone have an understandable proof for the integral of 2^x being (2^x)/ln2? Is it something we need to be able to prove?
The proof is through method of substitution. So let 2^x = t and integrate , you should be able to prove why the final answer is /ln(2)
4. I have only just found out about the rule which stops you from having a mix of applied units in your normal maths alevel (eg: D1 in AS can't be followed by M2 in A2)

However is it possible to have this combination:

Maths- D1 in AS then M1 in A2
Further- S1 and S2 in AS then M2 and S3 in A2

??
5. prove
cot2x + cosec2x = cotx

in two simple steps
6. (Original post by XxKingSniprxX)
You mean Edexcel C4 June 15?

I did that paper last year and got 62/100 (c) ums.
I remember dropping marks everywhere.

Just make sure you work hard on all areas on C4 & that you've seen
literally everything, especially for that last question that threw everyone off.

In my opinion, only hardest bits on that paper are: last q on the vectors (if you drew a clear diagram its simple), that implicit differentiation question where you have to times on through on the left @y and that realise integrating 2^x = 2^x/ln(2)

Keep at it, don't let 1 paper performance stop you. Just realise where you dropped marks and your mistakes and move on.
Yhh, I agree, the differentiation one was wierd. Hopefully I can improve on my mistakes, thanks man
7. (Original post by Pablo Picasso)
prove
cot2x + cosec2x = cotx

in two simple steps
cot2x + cosec 2x = (cos2x)/sin2x +1/sin2x
=(2cos^(2)x)/2sinxcosx
=cosx/sinx
=cotx
8. (Original post by NotNotBatman)
cot2x + cosec 2x = (cos2x)/sin2x +1/sin2x
=(2cos^(2)x)/2sinxcosx
=cosx/sinx
=cotx
Thats 4 steps
9. (Original post by Pablo Picasso)
prove
cot2x + cosec2x = cotx

in two simple steps
cot 2x + cosec 2x = cos x / sin x = cot x
10. (Original post by Snasher350)
I have only just found out about the rule which stops you from having a mix of applied units in your normal maths alevel (eg: D1 in AS can't be followed by M2 in A2)

However is it possible to have this combination:

Maths- D1 in AS then M1 in A2
Further- S1 and S2 in AS then M2 and S3 in A2

??
Yes.

But don't worry, Edexcel sorts out how your units go where (provided your school has re-cashed everything in or whatever, but that's something you don't need to worry about if your school offers Further Maths as a taught subject.).
11. (Original post by Zacken)
cot 2x + cosec 2x = cos x / sin x = cot x
12. Anyone have the 2016 IAL C34 paper?
13. . Why is it every time I'm doing a seperating the variables question it seems like the side you take the constant to is guesswork?

e.g, dy/dx= KY.

From there you can either do:

the intergral of 1/Y = The intergral of K.

Or you can do:

The intergral of 1/KY= The intergral of 0 (Edit: I meant 1 here, not 0)

There are some questions where it doesn't matter at all and you'll easily get the same "C" + same final solution regardless of which way you did it. Yet there are other questions where it completely over complicates your answer if you do the one that Edexcel didn't want. It genuinely pisses me off. Am I missing something (or messing up an easy step)? Or is it that just how it is?
14. (Original post by lucabrasi98)
. Why is it every time I'm doing a seperating the variables question it seems like the side you take the constant to is guesswork?

e.g, dy/dx= KY.

From there you can either do:

the intergral of 1/Y = The intergral of K.

Or you can do:

The intergral of 1/KY= The intergral of 0

There are some questions where it doesn't matter at all and you'll easily get the same "C" + same final solution regardless of which way you did it. Yet there are other questions where it completely over complicates your answer if you do the one that Edexcel didn't want. It genuinely pisses me off. Am I missing something (or messing up an easy step)? Or is it that just how it is?
There's a problem if you think that dividing both sides by KY gives you 0...

if you have: dy/dx = ky

then this can be the same thing as integral of 1/(ky) dy = integral of 1 dx.
15. (Original post by Zacken)
There's a problem if you think that dividing both sides by KY gives you 0...

if you have: dy/dx = ky

then this can be the same thing as integral of 1/(ky) dy = integral of 1 dx.
Oh that's what I meant. Not sure why I typed in 0. But the point stands, doing it either way vastly changed how difficult it it to get what's in the mark scheme.
16. (Original post by lucabrasi98)
Oh that's what I meant. Not sure why I typed in 0. But the point stands, doing it either way vastly changed how difficult it it to get what's in the mark scheme.
You're probably just missing an easy step, then. Post your working for an example.
17. Edexcel Maths IAL C34 June 2015 = 110/125 raw marks = 98% = A*
I could have scored 115-117/125 raw marks if I didn't make stupid mistakes. The other questions I wouldn't
have gotten them even if I tired

Grade boundaries: 100% = 113, A* = 101, A = 89, B = 77, C = 65.

Mistakes:
- Finding the range of the graph (-2 raw marks)
- Misread working out due to little space on page. ( -1 raw mark)
- Reverse differentiation to prove a formula (alternative method) forgot to 1/4 or realised that simple connection. (-1 raw mark)
- Had no *censored* clue that the value of t= -3 was consistent on B when it meets at point X ... I knew the long division method if I had known that but even then it was t = -3, t = -3 .*. (t-3)^2 <-- no clue (-4 raw marks)
- Failed to read the question said "find the times" and not "time" and due to
not drawing a quadrant diagram I didn't see the other value of theta. (-3 raw marks)
- I had no clue on how to solve the vectors question and only knew that if a vector is parallel it is a scale factor of the other I.e ' k . direction vector (i,j,k) ' <-- Someone please confirm thats right just encase.
(-4 raw marks)

Notes:
- Remember: ln(e) = 1, ln(1) = 0, ln(0) = no solutions.
- Remember volume of revolution: pi. integral (y^2) . dx [look at the equation otherwise use substitution]
- Remember how to integrate ln(x) by putting ' 1ln(x)' and then using parts.
- Draw quadrant diagrams + note down carefully & underline any +/- values.
- Notice the units of rates of change problems to see if its 2 parts or 3 parts involved.
- Remember: e^1-10k is equivalent to e^1 . e^-10k & other examples.
- Simplify the answer as much as possible as it may make life easier on the next part.
- REALISE MIDDAY = 12pm and MIDAFTERNOON = 3pm.

Spoiler:
Show
Past papers left to do: Jan 2016 C34 IAL, x3 C3 MAM paper (x1 hard + x2 hardest)
+ x7 C4 MAM papers (hard to very hard difficulty)

Spoiler:
Show
Life is so scary when you need 95% ums in 2 papers = A* otherwise you'll be moving away from home comforts & most importantly depressed about 'what ifs'
18. Just have a guy feeling the vectors question next week will be tricky :/

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19. (Original post by DDan123)
Just have a guy feeling the vectors question next week will be tricky :/

Posted from TSR Mobile
Draw a clear labelled diagram and drink lots of caffeine
20. (Original post by Zacken)
You're probably just missing an easy step, then. Post your working for an example.

It's question 8 on C4 Gold paper 3.
You were right. http://m.imgur.com/tSdOM7l,lkD5FxG

I was obviously making a stupid mistake somewhere. It still changes the value you get for the constant though. Plus it makes the working out more confusing. It also isn't even on the mark scheme. The final solution is but all of the working out isn't. I don't know how much I'd be credited.

I just wish there was a way to know which one Edexcel wanted people to use so i didn't have to spend an extra few minutes on what should be an easy question. The one with 1/KP in this case has more room for error too

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