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Edexcel FP1 Thread - 20th May, 2016

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Original post by economicss
Not very far at all, only got the equation! Please could you post your working for it :smile: have you done part b? Thanks :smile:


Did you see my working out I posted earlier?

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Original post by fpmaniac
Can you properly explain to me how to do sigma r=0 to r=n with some examples. I still dont get it....


Remember

∑i=0nf(i)=∑i=1nf(i)+f(0) \displaystyle\sum_{i=0}^n f(i) = \displaystyle\sum_{i=1}^n f(i) + f(0)

That's all you need to know. You want to just get a 1 at the bottom, so that you can then use your standard formulae :smile:
Original post by Hot&SpicyChicken
Well im going to die!
Can you help with the induction for Jan 2016 IAL Quesiton 9?

Thanks much apreciated!


What have you tried?
question: for the argument of z

i know you do tan^-1 (b/a) of a + bi

but do you keep a and b exactly how they are, or are they the mod of a and b?

example:
z = 1 - i

would it be tan-1(-1/1) or simply tan-1(1/1)... and why?
Original post by TomWeller
question: for the argument of z

i know you do tan^-1 (b/a) of a + bi

but do you keep a and b exactly how they are, or are they the mod of a and b?

example:
z = 1 - i

would it be tan-1(-1/1) or simply tan-1(1/1)... and why?


I find it easiest to draw z on an Argand diagram and use tan-1 of the mod of b/a, then draw on the diagram which angle you've calculated and from that work out the argument of z
Original post by TomWeller
question: for the argument of z

i know you do tan^-1 (b/a) of a + bi

but do you keep a and b exactly how they are, or are they the mod of a and b?

example:
z = 1 - i

would it be tan-1(-1/1) or simply tan-1(1/1)... and why?


You should compute a and b without their signs and then use the signs (and an Argand diagram, I hope) to determine what the argument will be.

For example, -2-3i, will be worked out -pi + arctan(3/2), and 2+3i, just arctan(3/2).
I dont understand what to use when doing proof for divisibility.

Do you prove for f(k+1) then prove thats divisible by x
or do you prove f(k+1)-f(k) is divisible by x
or do you prove f(k+1) -nf(k) is divisible by x?

How do I know which to do?
Original post by kingaaran
You should compute a and b without their signs and then use the signs (and an Argand diagram, I hope) to determine what the argument will be.

For example, -2-3i, will be worked out -pi + arctan(3/2), and 2+3i, just arctan(3/2).


Thank you! i think there may a mistake on one of my teacher's worksheets which is annoying which uses a and b exactly how they are with the negative sign. Thank you
Original post by fpmaniac
So what would it be for sigma r=0 r=n for r and sigma r=0 and r=n for rsquared


Well, think about it.. how many terms are there from r = 0 to n?
Original post by kingaaran
Solution on post 940


ahh thank you!!
Original post by AlfieClements
I dont understand what to use when doing proof for divisibility.

Do you prove for f(k+1) then prove thats divisible by x
or do you prove f(k+1)-f(k) is divisible by x
or do you prove f(k+1) -nf(k) is divisible by x?

How do I know which to do?

Always write f(k+1) and then aim to find f(k) within the equation
Can someone post a couple of tricky FP1 questions? The past papers are very repetitive. :frown:
Original post by hogree
Question.

When you differentiate a parabola (so something with the equation y2 = 4ax) would you always make the differential a +/- or would you put it as simply a +? Because if leaving it just as a +, it gives you just one equation when you plug in, because obviously there is just one gradient.. But a +/- makes more sense.

Anyone mind clearing this up?


Take the + because you're normally only concerned with the bit above the axis.
Original post by techfan42
Always write f(k+1) and then aim to find f(k) within the equation


Okay, then if it doesn't work should I do f(k+1) - f(k)?
Original post by Hot&SpicyChicken
Well im going to die!
Can you help with the induction for Jan 2016 IAL Quesiton 9?

Thanks much apreciated!


sorry for the ink smudge
fp1 question.jpg288.0KB
Original post by alfmeister
Did you see my working out I posted earlier?

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No, could you link me to it please? Thanks :smile:
Original post by AlfieClements
Okay, then if it doesn't work should I do f(k+1) - f(k)?


It always works. I used to do f(k+1) +/- f(k), but then used to get the questions wrong sometimes. This is much easier as it always works also it's the method always used in the FP1 model answers
Original post by alfmeister
Did you see my working out I posted earlier?

Posted from TSR Mobile


Ah just found it, thanks so much for that :smile: I don't suppose you've done part b? Thanks :smile:
Can somone answer June 2010 Question 7a for me ?


I dont get the answers on the MS


Cheers
Original post by fpmaniac
Where did the 2n come from in the end equation. If u add r=0 shouldnt it be just +2


As 2n is the sum of 2 to n numbers and as it is r^2 +2 then for the sum you need to add 2n.
With the r=0 you just add whatever the series equals when 0 is put in. For my example I added 2

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