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

1. (Original post by economicss)
Please could anyone explain how to do question 19b and 19d here, really struggling with them! Thanks Attachment 540593
Hi, did you figure this q out completely?

for b, i got x = -1

for d i, i got Z = 1/2 + 3/2 i

Are these correct? Thanks
2. Can someone help me with these types of question:
sketch the locus of z when: arg((z-3i/(z+4))=pi/6

Ive never seen a question like this come up in a past paper but this is from the textbook so I guess this means we need to know how to do it....
3. https://8dedc505ac3fba908c50836f5905...%20Edexcel.pdf

5b, i get that we took a point z = 0 + 0i and plugged it in w, and got w =0 - how does this tell us it maps to inside of the circle?
4. (Original post by imnoteinstein)
https://8dedc505ac3fba908c50836f5905...%20Edexcel.pdf

5b, i get that we took a point z = 0 + 0i and plugged it in w, and got w =0 - how does this tell us it maps to inside of the circle?
edit: To see it more clearly, imagine swapping the = for inequalities earlier on (making sure to use the appropriate rules for changing the direction if required)
Basically the circle is like a boundary for the mapping. So if one point is inside, then they all are; if one is outside, then they all are.
5. Hi, i could find this question inthe thread so i thought that i would post it.

Question 5 of fp2 june 2013 (withdrawn) is troubling me.

I can get the partial fractions just fine and.lay out the series the way they do.

To me it looks like the final part should be 1+0.5 not 1-0.5, i am looking at the second row of the expanded series
6. (Original post by 13 1 20 8 42)
edit: To see it more clearly, imagine swapping the = for inequalities earlier on (making sure to use the appropriate rules for changing the direction if required)
Basically the circle is like a boundary for the mapping. So if one point is inside, then they all are; if one is outside, then they all are.
ohhhh i see, so if id put in 0 and w was something >radius, that would mean its outside the circle?
7. (Original post by fizzing)
Can someone help me with these types of question:
sketch the locus of z when: arg((z-3i/(z+4))=pi/6

Ive never seen a question like this come up in a past paper but this is from the textbook so I guess this means we need to know how to do it....
Examsolutions explains it well
8. (Original post by imnoteinstein)
ohhhh i see, so if id put in 0 and w was something >radius, that would mean its outside the circle?
Well since the circle is not centred at the origin it is a bit more complicated than that, as for instance you have -7/5,0 in this circle, but the absolute value of this is greater than the radius. In general it should be obvious whether or not the origin is inside a circle.
9. (Original post by fizzing)
Can someone help me with these types of question:
sketch the locus of z when: arg((z-3i/(z+4))=pi/6

Ive never seen a question like this come up in a past paper but this is from the textbook so I guess this means we need to know how to do it....
10. (Original post by alvosm)
sorry but i was wondering why i can't see many of the pictures you guys post. Can anyone help me with this? is it my computer? thanxx
TSR is just being buggy today. It'll be fixed soon enough. (they're not pictures btw, they're code to generate maths expressions)
11. Help with this question please
excercie 3.6 in FP2 OXBOX Textbook
Question 14(a)
Point P in the argand diagram represents the complex number z where arg((z-1-2i)/(z-2i))= pi/2
(a) use a geometrical approach to show that the locus of p never does not intersect imaginary axis.
Hint : Use a fact true of all triangles.
12. if arg(z) - arg(z1) = pi/4
does that mean arg(z1) - arg(z) = -pi/4 ?
13. (Original post by AmarPatel98)
sometimes they say d/d(theta) but this will be the same thing as differentiating the function y=r sin(theta) or x = r cos(theta).

They just havent put dy/d(theta) but it's the same thing.

As the previous person said,

dy/d(theta) = 0 for parallel to initial line
dx/d(theta) = 0 for perpendicular to the initial line
(Original post by maruchan)
do you mean when they say in the questions the line is parallel and perpendiuclar to the curve.

If it is parallel you do rsintheta=y then differentiate

If it is perpendicular you do rcostheta=x the differntiate

Hope that helps

Ah okay that makes a lot more sense, I will check out the book again see if it makes things even more clearer. Thank you!
14. I wonder if we'll get all the points for writing down the solution for a relatively simple partial fraction.
15. from 2015 paper, question 1b, i can do the first part fine but how do i do the 1 marker after it? seen it come up on a few papers now, model answers dont answer it correct
16. (Original post by AakashG)
if arg(z) - arg(z1) = pi/4
does that mean arg(z1) - arg(z) = -pi/4 ?
Yes.

(Original post by EricPiphany)
I wonder if we'll get all the points for writing down the solution for a relatively simple partial fraction.
I think you do.

(Original post by connorbarr)
from 2015 paper, question 1b, i can do the first part fine but how do i do the 1 marker after it? seen it come up on a few papers now, model answers dont answer it correct
Consider x > -3 and x < -3 The former gets you the same inequality in (a)
17. (Original post by EricPiphany)
I wonder if we'll get all the points for writing down the solution for a relatively simple partial fraction.
You do.

18. the only proof we have to know is the de moivre's?
19. Could someone explain this please?
Attached Images

20. (Original post by Chirstos Ioannou)
Could someone explain this please?
Just basic algebra using modulus function, they have skipped steps
Write out w in terms of real and imaginary components, separate them within each modulus, then use standard rules of modulus

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