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# Edexcel C3,C4 June 2013 Thread watch

1. (Original post by PythianLegume)
With integration and differentiation, it's generally radians. Also, think about the values in that question - if it asks about 2 weeks, when t=2, you're not going to be doing sin of 1 degree.
Thanks, didnt think of it like that.
2. (Original post by suncake)
Say you have something like this... Can you just take out 1/3 as a factor and put it outside the integral?
Attachment 227729

Posted from TSR Mobile
Yes, I would do that to simplify the question.

(Original post by PhoenixSeeker)
I still can't get it to work is it possible to do it this way?
I'm fairly sure you can't do it that way with C4 techniques.
3. (Original post by Story)
Yeah. I did 1/cos^2x = 1/(1/2cos2x+1), then when flipping it I think I made an error as I wrote 2/2cosx+1..but does the half become a 2 or is it just 1/2....Is it 2(cos2x+1)..?
Firstly, cos^2(x) = 1/2cos2x + 1/2! But I don't get how you're flipping it?
4. (Original post by orange94)
You mean like this ?

Attachment 227728

Posted from TSR Mobile
As Maths 247 put it,

Let them get married! ( i dont think you have done anything wrong?)
5. (Original post by suncake)
Say you have something like this... Can you just take out 1/3 as a factor and put it outside the integral?
Attachment 227729

Posted from TSR Mobile
6. (Original post by justinawe)
(Original post by PythianLegume)
Well y=32x

ln(y) = 2xln(3)
(1/y)(dy/dx)=2ln(3)
dy/dx=2 x 32xln(3)

Hence integration divides by 2ln(3).
Ohhh I get it - thanks! Is this in the syllabus btw? Haven't come across it much before :s
7. (Original post by Myocardium)
Ohhh I get it - thanks! Is this in the syllabus btw? Haven't come across it much before :s
The differential of a^x is definitely in the syllabus.
8. (Original post by frogs r everywhere)
Reminds me of good ol' GCSE days.

Pretty colours everywhere.
9. Thank you so much!
10. (Original post by Kardy)
Form simultaneous equations to find lamda. The two equations can be formed from the dot product of l1 & AP (which are perpendicular so = 0 ) and the other equation you already have, it's the equation of the line l1.

http://www.examsolutions.net/a-level...7&solution=7.3

Thanks Kardy so much..!!!!!!!!!
Good luck tomorrow...!!!!!
11. (Original post by Myocardium)
How would you integrate something like 3^x?
This is the 3rd time this has been asked today ( I asked first), everyone will be able to do this in their sleep now, ha ha just remember when you differentiate you get 3^x.ln3 but when you integrate you get 3^x/ln3

EDIT: Don't ever forget the +c
12. (Original post by frogs r everywhere)
Multiply by k, Take exponentials, Get rid of the denominator by multiplying through, Expand brackets and take it from there.

but I have two k's though so I can't multiply out until I have taken e to both sides...
13. (Original post by Westeros)
I think you can. Why would you not just take 1/3 out?
14. (Original post by suncake)
Say you have something like this... Can you just take out 1/3 as a factor and put it outside the integral?
Attachment 227729

Actually, could someone work through this for me Death by lns...

Posted from TSR Mobile
Well I did! You right!

Unless anyone here objects to 1/3 being pulled out.

Here is what I did

Posted from TSR Mobile
15. (Original post by Myocardium)
Ohhh I get it - thanks! Is this in the syllabus btw? Haven't come across it much before :s
Page 41 in your Edexcel C4 textbook

(Original post by Supes180)
I think you can. Why would you not just take 1/3 out?
Hmm, I don't know. I'd just approach it this way because it's easier for me

(Original post by lefterispower)
Yeaa i know that...but i dont know the steps before doing a.b=0

if you have time to write me the solution i would be so happy...
https://www.youtube.com/watch?v=ROC5tCZWPRs This video explains it all!
16. (Original post by imasha.sj)
Thank you but why use the two t values for x=2.5 instead of using the t values for x=2 and x=2.5?
I didnt try to find the t values for x. did you? i dont think there is a suitable value :/ It made sense when i drew a vertical line at x=2.5 and marked the points where x=2.5 cuts the curve ( upper point being t= 2 and lower t=.5 ) As long as the area is bounded by values you are aware of, you can integrate! Over here we used t, because we had already found its values. I didnt really try changing x= 1 and x=2.5 to t. too much working :P
17. (Original post by orange94)
Well I did! You right!

Unless anyone here objects to 1/3 being pulled out.

Here is what I did

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Integral of 2/(2x-1) you wrote as ln|2x-1| is this correct?
Also don't forget +C on your second line
18. I can't believe after doing hundreds of integration questions I still manage to completely forget about the c argg
19. I've no idea how to draw graphs from parametric equations. Eek
20. (Original post by Westeros)
Integral of 2/(2x-1) you wrote as ln|2x-1| is this correct?
Do you think it isn't? One of us is missing something here.

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