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# Edexcel A2 C4 Mathematics June 2015 - Official Thread watch

1. (Original post by Egg1)
Where did you actually learn this? As I've never seen it in my book, makes me worried there'll me more stuff like this theyll give us that I will have just never seen before haha

Also why does the integral of a^xlna = a^x ?
I didnt learn it. I recongnised.
Integratinf from left to right is differentiating from right to left lol.

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2. How many marks do you think something like that would be?
Im thinking 5 or 6, it seems very long winded.
3. Hi guys! Any tips for remembering all the methods for solving integrals?
4. (Original post by Boro12345)
I am absolutely ******. What should I focus on? I can do binomial, partial fractions, and basic integration, and a lot of vectors.
why are you f**** then? Do you mean you can or you can't? lol
5. (Original post by Senll)
Any suggestions on mastering vectors?

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If a questions over 4 marks, always draw a diagram.
6. (Original post by Johann von Gauss)
There's no leeway in the syllabus for revolutions for basic revolutions around different lines? Where's the fun in just revolving around y=0 all the time?
Easy for the norms peopoles.

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7. (Original post by rory58824)
Hi guys! Any tips for remembering all the methods for solving integrals?
Knowing when a function can be integrated or when it has to be modified, especially in trig functions.

Knowing the integrals of functions rarely seen in past papers, such as ax

Knowing more then one method of integrating, especially in substitution, and using recognition to see what method will be best suited.

And the best tip is to probably expose yourself to various different questions, but i guess its kinda too late for that now.
8. can you leave vectors as column vectors or do you need to put in i+j+k form?
9. Hey friends
I need help

I know what the values of sin cos and tan of 30,45 and 60 are because I've used them so many times I know them by heart but I'm not sure how to find values of other angles eg 120 which is sometimes needed in integration when you need to simplify your answer (my calculator does not give them in this fraction form) my teacher told me in one particular question that had sin 2π/3 that I can just use 180-60 and figure it out like that but what if it's cos or tan?
10. (Original post by alexboulton)
can you leave vectors as column vectors or do you need to put in i+j+k form?
if they don't specify it doesn't matter
11. (Original post by candol)
The idea has come up before.
eg 2x differentiates to 2xln2.
that means if i am integrating (going the other way) 2x the answer must be something to do with 2x . It is just a matter of sorting out the constant.
So integrate 2x ln2 becomes 2x
therefore integrating 2x becomes 2x/ln2
Oh right ok thanks!
12. (Original post by angelonm)
Hey friends
I need help

I know what the values of sin cos and tan of 30,45 and 60 are because I've used them so many times I know them by heart but I'm not sure how to find values of other angles eg 120 which is sometimes needed in integration when you need to simplify your answer (my calculator does not give them in this fraction form) my teacher told me in one particular question that had sin 2π/3 that I can just use 180-60 and figure it out like that but what if it's cos or tan?
Use CAST diagrams
or find a better calculator
13. (Original post by angelonm)
Hey friends
I need help

I know what the values of sin cos and tan of 30,45 and 60 are because I've used them so many times I know them by heart but I'm not sure how to find values of other angles eg 120 which is sometimes needed in integration when you need to simplify your answer (my calculator does not give them in this fraction form) my teacher told me in one particular question that had sin 2π/3 that I can just use 180-60 and figure it out like that but what if it's cos or tan?
learn CAST diagram approach or become familiar with the graphs and simple properties of the graphs
Use CAST diagrams
or find a better calculator
yo i aint got no time to find a better calculator the exam's tomorrow
I know I'm supposed to use CAST diagrams but I don't get how
15. (Original post by angelonm)
yo i aint got no time to find a better calculator the exam's tomorrow
I know I'm supposed to use CAST diagrams but I don't get how
well generally you can use the approach that sinx = sin (180-x) and cos x = cos(-x)
also for sin 210, draw a cast diagram. you'll see that sin210 = -sin30
16. is it me or is it so much easier to make stupid mistakes in C4 than C3?
17. (Original post by Jimmy_M)
Well the =36 suddenly disappeared on the line when you /9. You did it all correct, except it should be 225-36, which is 189, then divided by 9 you get 21, meaning the answer is lamda = -3 or -7

Oh no I see, you did do the cancelling correctly. I got an equation same as yours excep =36.. I'm unsure how you got to that stage if I'm honest..
I got the 36, because I'm applying Pythagoras for the distance between two points. The distance between them is 6, which by the formula I should make 6^2? :/

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18. (Original post by Bustamove)
is it me or is it so much easier to make stupid mistakes in C4 than C3?
Agreed

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well generally you can use the approach that sinx = sin (180-x) and cos x = cos(-x)
also for sin 210, draw a cast diagram. you'll see that sin210 = -sin30
Ok! Thanks so much
20. (Original post by Johann von Gauss)

I prefer using simple formulae to the CAST diagrams;
sin(x) = sin(180-x), sin(x)=-sin(-x)
cos(x) = -cos(180-x), cos(x) = cos(-x)
will do everything the CAST diagrams do, and are much more efficient.
thanks non friend!

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