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Edexcel FP1 Thread - 20th May, 2016

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Please could you post a pic or link to the distance from the focus and directrix formula, not sure I've come across it, thanks :smile:

There is this one.

Also this:

Focus:

(a, 0)

, Directrix:

x = -a

, General point:

(at^2, 2at)

Distance from general point to focus:

S^2 = (at^2 - a)^2 + (2at)^2 = a^2 (t^4 + 2t^2 + 1) = a^2 (t^2 + 1) \implies S = a(1+t^2)

Distance from general point to directrix:

D = a + at^2 = a(1+t^2)

\therefore S = D

(edited 7 years ago)

Reply 721

Pyslocke

Original post by NotNotBatman

What about r then?

r is also positive it says

Reply 722

NotNotBatman

Original post by Pyslocke

r is also positive it says

oops, didn't read the question properly.

Reply 723

Louisb19

Original post by SLamb

For proof's by induction, when the question asks to prove that _____ is divisible by X, are we allowed to use the general rule that (M^n -1) is always divisible by (M-1)? I've done that in a couple of recent assessments and been marked correct but i thought I'd be better safe than sorry

You can factorise like this

a^n - b^n = (a - b)( a^{n-1} + a^{n-2}b + ... ab^{n-2} + b^{n-1} )

There is also this one:

a^n + b^n = (a + b)( a^{n-1} - a^{n-2}b + ... )

(edited 7 years ago)

Reply 724

SLamb

Original post by oinkk

Ah, that's quite handy. I'm guessing that would work for any angle of rotation.

Yup, if the angle is less than 180, you don't need to subtract, but if it's greater than 180 you will :smile:

Reply 725

Chirstos Ioannou

Original post by Genius123456

Try this hard question and reply by sending the solution if you solve it. The hardest one you can get. I could not solve it
Thanks in advance

There you go mate, i hope you can see what i wrote. By the way, which paper is that?

Reply 726

SLamb

Original post by Louisb19

You can factorise like this

a^n - b^n = (a - b)( a^{n-1} + a^{n-2}b + ... + b^{n-1} )

Ahhhhhh, that explains it for me aha, thanks!

Reply 727

anakinlong

Hope this helps:

https://gyazo.com/2ee29fccfbcb4d0663d07939320ad106

Reply 728

Louisb19

Original post by SLamb

Ahhhhhh, that explains it for me aha, thanks!

Its the method that I used for Jan 2014 IAL 10 ii).

Their +- way was cool too though.

Reply 729

Yua

how would i do part b

Reply 730

anakinlong

Original post by iMacJack

ImageUploadedByStudent Room1463651006.567317.jpg

hey I can't seem to get this proof right, please give some assistance Zacken or anyone!!

Posted from TSR Mobile

Hope this helps:

https://gyazo.com/2ee29fccfbcb4d0663d07939320ad106

You can do pretty much all of the "prove f(n) is divisible by x" questions like this, by getting expressions for f(k) and f(k+1), then getting an expression for f(k+1) in terms of f(k). Since you've already assumed f(k) is divisible by "x", the rest of the expression should just work itself out.

Reply 731

BRBBIT

Guys, do the international papers include anything that the normal ones don't?

Reply 732

Zacken

Original post by BRBBIT

Guys, do the international papers include anything that the normal ones don't?

Roots of polynomials with the alpha, beta stuff is in the international paper but isn't on the UK spec.

Reply 733

economicss

Please could anyone explain how to do question 9c on here http://www.thestudentroom.co.uk/attachment.php?attachmentid=72189&d=1244566570 as the mark scheme doesn't show a method, thanks :smile:

Reply 734

hogree

Original post by Chirstos Ioannou

There you go mate, i hope you can see what i wrote. By the way, which paper is that?

Smart smart smart... Cheers for that.

Reply 735

economicss

Original post by Louisb19

There is this one.

Also this:

Focus:

(a, 0)

, Directrix:

x = -a

, General point:

(at^2, 2at)

Distance from general point to focus:

S^2 = (at^2 - a)^2 + (2at)^2 = a^2 (t^4 + 2t^2 + 1) = a^2 (t^2 + 1) \implies S = a(1+t^2)

Distance from general point to directrix:

D = a + at^2 = a(1+t^2)

\therefore S = D

Thanks so much :smile:

Reply 736

SLamb

Original post by Yua

how would i do part b

Once you've worked out the angle in part a) (should be 225?) You can then do 360 / (225-180) = 8, so n=8

Reply 737

TheRandomGenius

Has anyone got any hard(er than usual) FP1 questions/ papers? I have done all the papers including IAL and the textbook review exercises and am struggling to find revision material...

Reply 738

TheRandomGenius

That question is from the old FP1 spec; it includes 'e', which is introduced in C3 whilst the new FP1 spec only assumes C1,C2 knowledge. You therefore don't need to be able to do it.

Original post by economicss