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# Edexcel FP2 Official 2016 Exam Thread - 8th June 2016 watch

1. (Original post by oinkk)
What happens when we're finding a Maclaurin expansion of a function and when it comes to evaluating a particular part of it, we end up doing 1/0?
Do you have a specific question?
2. (Original post by Craig1998)
Do you have a specific question?
Nah. I was just considering that scenario. Take y = cosec x for instance.
3. (Original post by oinkk)
What happens when we're finding a Maclaurin expansion of a function and when it comes to evaluating a particular part of it, we end up doing 1/0?
Not possible. For a MacLaurin expansion to be valid (i.e: for it to exist) you require all derivatives to be defined. i.e: if you get get 1/0, it means you're working out the Maclaurin series of a function that doesn't have a MacLaurin series. (like ln x)
4. (Original post by oinkk)
Nah. I was just considering that scenario. Take y = cosec x for instance.
You won't get 1/0, but you could a term which is 0, in which case you skip it and move to the next one.
5. (Original post by TheMarshmallows)
if its a "show that" question, then you can use the answer whilst solving it (to show that it is true). Generally using u+iv will work always, doing it with modulus' is usually less algebra/shorter but isn't always possible (and takes some thinking).

For example in the question we were talking about before, arg(z) = pi/4 is the half line y=x, so you can rewrite z = x + iy into z = x + ix (or z = y + iy if you prefer, it doesnt matter).

Then subbing into W = (Z+1)/(z+i) we get W = (x + ix + 1)/(x + ix + i)
grouping real and imaginary gives W = ( (x+1) + ix ) / (x + i(x+1) )

Looking at the answer, they want you to show that mod(W) = 1 so mod(our W) = 1

mod( (x+1) +ix) / (x + i(x+1)) ) = 1

mod((x+1) +ix) / mod(x+ i(x+1)) = 1

Remembering that mod(a + ib) = sqrt(a^2 + b^2) gives us

sqrt( (x+1)^2 + x^2) / sqrt( x^2 + (x+1)^2 ) = 1

which is clearly true because they're the same thing.
Thanks. What do you think I should use in the exam, u + vi or x+yi. With u+vi you have to take long steps but its more straightfoward I guess but x+yi is easier but I might not get it . I also take long time to finish other questions so i dont know...
6. (Original post by Zacken)
Not possible. For a MacLaurin expansion to be valid (i.e: for it to exist) you require all derivatives to be defined. i.e: if you get get 1/0, it means you're working out the Maclaurin series of a function that doesn't have a MacLaurin series. (like ln x)
Understood! Cheers.
7. Hey have you guys done the review 1 ex in the FP2 book.
I m struggling with q47 pg70- could that come up tomorrow
8. (Original post by fpmaniac)
Thanks. What do you think I should use in the exam, u + vi or x+yi. With u+vi you have to take long steps but its more straightfoward I guess but x+yi is easier but I might not get it . I also take long time to finish other questions so i dont know...
I'd stick with what you know and what you feel comfortable doing rather than trying to change methods now.
9. (Original post by Inges)
http://imgur.com/xKBlDyE

Hope this helps, it really brain teasing I know!
(Original post by edothero)
Product rule with and

Thank you both very much!
10. (Original post by Anon-)
guys, could someone please explain the questions where they ask you to shade the area after a transformation in the complex plane? June 2009 6b or June 2015 5b for example
bump
11. (Original post by economicss)
Please could anyone do a worked solution for question 12a https://8dedc505ac3fba908c50836f5905...%20Edexcel.pdf I've tried it by substituting in for lambda plus lambda i when x is greater than 0 but for some reason I can't get it to work but I thought the method was correct? Thanks
do you have any similar questions? i need to practice these ones!
thanks
12. (Original post by Cpj16)
Hey have you guys done the review 1 ex in the FP2 book.
I m struggling with q47 pg70- could that come up tomorrow
I'm almost certain that won't come up.
13. (Original post by oinkk)
Nah. I was just considering that scenario. Take y = cosec x for instance.
I think this is the reason we are given the expansion for ln(1+x) rather than lnx. It just wouldnt work.
14. (Original post by Anon-)
bump
Test out a point and see what it is transformed to, if it is in the circle then you shade inside, if it is outside the circle, you shade outside. If that doesn't satisfy you, just look through your calculations and mentally replace the = with the appropriate inequalities and see what inequality you're left with at the end.
edit: Ah I see you were talking generally, but in practice it's usually circles..

15. Can someone please assist on 2c it got messy when trying to mod it.
16. (Original post by Anon-)
bump
Pick a point (z) that satisfies whatever you have, then use the transformation to turn it into W and look at where that point is on the graph. For example in June 2015 5B:

mod(z) <= 2

pick a point that satisfies this. Easiest point is z = 0 + 0i

w = z/(z+3i) = 0/(0+3i) = 0

w = 0 + 0i is inside of the circle from part a, so you shade inside of the circle.

17. 11c I got all wrong can someone post a solution to this, thanks.
18. (Original post by TheMarshmallows)
I'm almost certain that won't come up.
In fairness, it was on a past edexcel exam (old spec FP2 I believe).

These can often become easier if you multiply through by e^-0.5iø to get something with cos0.5ø on the bottom; there on it is but algebraic manipulation and using trigonometric formulae.

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19. (Original post by TheMarshmallows)
Pick a point (z) that satisfies whatever you have, then use the transformation to turn it into W and look at where that point is on the graph. For example in June 2015 5B:

mod(z) <= 2

pick a point that satisfies this. Easiest point is z = 0 + 0i

w = z/(z+3i) = 0/(0+3i) = 0

w = 0 + 0i is inside of the circle from part a, so you shade inside of the circle.
yeah that's what I thought, thanks!
20. Can someone help me with this:

http://www.thestudentroom.co.uk/show....php?t=1612404

I've commented on it so can someone plssssss help

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