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# Edexcel Core 3 - 21st June 2016 AM watch

1. (Original post by Tow)
Jw. Someone posted this:
http://www.thestudentroom.co.uk/atta...6&d=1466461962

for d) would you look at when cos does 2 repeats and then find t for that, assuming you let theta = pi(t)/5?
I remember this was our mock paper in Year 13. It seems your reasoning is correct.
2. (Original post by 13 1 20 8 42)
I remember this was our mock paper in Year 13. It seems your reasoning is correct.
does that mean u do 4pi + alpha = pi(t)/5 ?
3. Am I right in thinking only a 'one to one' has an inverse function whereas 'many to one' and 'one to many' need restrictions to have an inverse function (like x>0)?
4. (Original post by Mathskid137)
Am I right in thinking only a 'one to one' has an inverse function whereas 'many to one' and 'one to many' need restrictions to have an inverse function (like x>0)?
whenever a question says 'why doesnt it have an inverse' write 'many-to-one'
5. (Original post by Tow)
does that mean u do 4pi + alpha = pi(t)/5 ?
Well, how I would think on it is like this. Two revolutions is 4pi radians, right? Hence you want to find t such that (pi*t)/5 = 4pi and this indeed yields the correct t value
6. (Original post by 13 1 20 8 42)
Well, how I would think on it is like this. Two revolutions is 4pi radians, right? Hence you want to find t such that (pi*t)/5 = 4pi and this indeed yields the correct t value
that's what I was thinking, hm... not sure why i put alpha in the equation... this was a half guess though. Didn't think about it enough. So I'm guessing the answer would be found through 4pi = pi(t)/5?
7. really hoping they serve us some nice trig questions
(Original post by ryandaniels2015)
thanks but does this not mean u have to show cast or graph?
9. (Original post by 13 1 20 8 42)
Well, how I would think on it is like this. Two revolutions is 4pi radians, right? Hence you want to find t such that (pi*t)/5 = 4pi and this indeed yields the correct t value
Also... if you don't mind, could you explain Q3c please?

http://qualifications.pearson.com/co...e_20130613.pdf

Not sure how/when the equation only has one solution.

10. Right the graph of cosx in that range has two solutions for every y value between 0 & 1, but only one solution for y=-1 and for y=1.
So set the cos part of the equation = to -1...
R(-1) = k, so k = -R
...and = to 1...
R(1) = k, so k = R

Or look at this...
https://07a69ccf283966549a9350d1a669...%20Edexcel.pdf
11. (Original post by khaleesi98)
Right the graph of cosx in that range has two solutions for every y value between 0 & 1, but only one solution for y=-1 and for y=1.
So set the cos part of the equation = to -1...
R(-1) = k, so k = -R
...and = to 1...
R(1) = k, so k = R

Or look at this...
https://07a69ccf283966549a9350d1a669...%20Edexcel.pdf
Ooooooooh yeah gotcha. Thanks! Goodluck for tomorrow!
12. (Original post by Tow)
that's what I was thinking, hm... not sure why i put alpha in the equation... this was a half guess though. Didn't think about it enough. So I'm guessing the answer would be found through 4pi = pi(t)/5?
Yah you literally just rearrange for t there.

(Original post by Tow)
Also... if you don't mind, could you explain Q3c please?http://qualifications.pearson.com/co...e_20130613.pdfNot sure how/when the equation only has one solution.
Man these are the ugliest and most boring questions around, but generally speaking you naturally use the Rcos(x-alpha) form derived, and here sketching a graph over the range 0 </=x < 360 degrees might be prudent
13. Goodnight guys and good luck!!
14. (Original post by 13 1 20 8 42)
Well, how I would think on it is like this. Two revolutions is 4pi radians, right? Hence you want to find t such that (pi*t)/5 = 4pi and this indeed yields the correct t value
Sorry why do you make pit/5 = 4pi. What has the pit/5 got to do with It all
15. Do you guys know when to use f '(x) to show a function is increasing or decreasing, and when to use f ''(x) ??
16. (Original post by Zacken)
If anybody needs any urgent help, feel free to tag me and I'll respond as soon as I can.
hi I just wanted to ask do you know which formules and Identities I need to learn of by heart for c3
17. (Original post by 5824)
Do you guys know when to use f '(x) to show a function is increasing or decreasing, and when to use f ''(x) ??
First derivative gives the gradient of the graph. If it yields a positive value at a particular x value, the function is increasing at that point, and vice-versa.

The second derivative is mainly used to find the nature of stationary points (minima or maxima). A positive second derivative value (with a first derivative value of 0) indicates a minima and vice-versa.
18. guys！！whwn is your exam time （uk time ）？？？mineis 8am

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19. I just completed the C3 June 2011 paper and got 80 something percent and for a C3 June 2015 paper I got 48/75, which I believe is 2 marks off an A since that paper was ridiculously hard. That's the highest I've got in the papers I completed today.

Anyways, good night guys and good luck! (Even though I don't believe in it ) I hope you all get the grades/marks you want and need.

(Original post by MaggieXUE)
guys！！whwn is your exam time （uk time ）？？？mineis 8am

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I think it is 9am for all students in UK.
20. (Original post by xdaryaxx)
hi I just wanted to ask do you know which formules and Identities I need to learn of by heart for c3
Nothing much, all the trig identities are given in the booklet.

Just remember sin (theta) = cos (90-theta), and vice-versa.

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