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OCR MEI FP2 Thread - AM 27th June 2016

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Quick question: When plotting points on an Argand diagram do you have to draw lines to the point from the origin? This is usually when plotting the roots of a complex number.

Don't think so, but if you have space perhaps label the points?

Like z = 1 + j

I don't think either of these are required though, unless asked or implied.

Reply 61

username1432214

This is very confusing. When its to do with eigen vectors and M. I know Mx=Yx ... but this makes no sense. M^2v and M^-1v ??
Someone please help. What even is M in these equations?

Jan 2012 Q3, eigen vector is displayed in answers and lambda =5

Do you replace M with lambda ??

Reply 62

Wunderbarr

Original post by HFancy1997

So worried about this exam, need an A for this...any predictions?

Posted from TSR Mobile

I predict questions on Polar Coordinates, Matrices, Complex Numbers and Hyperbolic functions.

Reply 63

TheBBT

Original post by Wunderbarr

Don't think so, but if you have space perhaps label the points?

Like z = 1 + j

I don't think either of these are required though, unless asked or implied.

thank you! I was never sure because some mark schemes have them and others don't, and I don't really see what the point of them is

Reply 64

username2640523

Original post by Wunderbarr

I predict questions on Polar Coordinates, Matrices, Complex Numbers and Hyperbolic functions.

I hope they come up too, ive prepared for those

Posted from TSR Mobile

Reply 65

Wunderbarr

Original post by TheBBT

thank you! I was never sure because some mark schemes have them and others don't, and I don't really see what the point of them is

If you draw the lines, it can be used to explain why the w³+w²+ w = 0 thing is true, by looking at the vector sum of the lines (if drawn as vectors going from the origin to Z).

Reply 66

Wunderbarr

Original post by Bealzibub

Do you replace M with lambda ??

My Matrices knowledge isn't the best, but I believe

Mv = \lambda v

So yes, perhaps treat M as lambda since it is suggested

M = \lambda

for an eigenvector

v

Reply 67

Wunderbarr

Does anyone know the polar graphs we're expected to remember? Specifically for those 2 markers?

Reply 68

username2640523

Original post by Wunderbarr

Does anyone know the polar graphs we're expected to remember? Specifically for those 2 markers?

You have to remember some??? Oh god, I hope not... ive just been plotting them for coordinates I get from my calculator

Posted from TSR Mobile

Reply 69

Wunderbarr

Original post by HFancy1997

You have to remember some??? Oh god, I hope not... ive just been plotting them for coordinates I get from my calculator

Posted from TSR Mobile

Well it's a lot quicker to remember the ones they may expect us to remember >_< .

Reply 70

username1432214

Can anyone help me with this:

ii) show that there is no positive integer n for which zn is imaginary.

In the mark scheme, I don't understand where kpi comes from?

(edited 7 years ago)

Reply 71

username1432214

Original post by Wunderbarr

Does anyone know the polar graphs we're expected to remember? Specifically for those 2 markers?

Nah, I just use table functino on calculation so I can plot the graph

Reply 72

Wunderbarr

Original post by Bealzibub

Nah, I just use table functino on calculation so I can plot the graph

Fair, fair.

Reply 73

MintyMilk

Original post by HFancy1997

You have to remember some??? Oh god, I hope not... ive just been plotting them for coordinates I get from my calculatorPosted from TSR Mobile

Original post by Wunderbarr

Well it's a lot quicker to remember the ones they may expect us to remember >_< .

Original post by Bealzibub

Nah, I just use table functino on calculation so I can plot the graph

Doesn't anyone else here use a graphic calculator?

Reply 74

username2640523

Original post by MintyMilk

Doesn't anyone else here use a graphic calculator?

Graphical calc? whats that? :wink:

Posted from TSR Mobile

Reply 75

username1432214

Original post by MintyMilk

Doesn't anyone else here use a graphic calculator?

No need for it at all, if you have decent casio calculator press MODE then 7 and you can use table mode, input a function specify a range for x values etc and it plots in a table for you. Then you can just plot the graph besides at most they are 2 mark questions anyway

Reply 76

MintyMilk

Original post by Bealzibub

Yeah I know that, I used a standard casio to do that for my AS exams. I still use that calc for exact values, but the Ti-84 Plus CE just opens up so many more possibilities with checking answers etc. It's also just nicer to use than any scientific calc

(edited 7 years ago)

Reply 77

Bruhh

Original post by Bealzibub

Can anyone help me with this:

ii) show that there is no positive integer n for which zn is imaginary.

In the mark scheme, I don't understand where kpi comes from?

Its imaginary if it's on the imaginary axis and so would have argument pi/2 or 3pi/2 the kpi bit just shows that you can add any multiple of pi and still be on the imaginary axis. It's like when you find roots of trig equations, there are infinitely many values if you just keep adding multiples of pi on etc.

Reply 78

username1432214

Original post by Bruhh

Do you understand this? If so could you please explain how to do ii) or anyone else for that matter. Here are my thoughts: since its centered at origin, the middle vertex must be touching the y axis somewhere. If one of the vertex is in 1st quadrant then I'm imagining a triangle like this (upside down):

Reply 79

Bruhh

Original post by Bealzibub

Since it's an equilateral triangle and you know one of the points, the other two can be found by rotating that point by 2pi/3 radians both clockwise and anticlockwise. So to find the other two points you'd multiply 2+4j by e^2jpi/3 and e^-2jpi/3. Then once you have those two points, you can use 1/2basexheight to work out the area.