# Edexcel A2 C3 Mathematics 12th June 2015Watch

This discussion is closed.
3 years ago
#641
the mark scheme follows the method but why would you do that I don't understand the thought process. Would you always do that if you have a question in this same format. Thanks

(Original post by 13 1 20 8 42)
Where is the mark scheme? I would just differentiate and set equal to zero and then isolate the e^x so as to take logs of both sides (and then conclude of course).
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3 years ago
#642
(Original post by humayra.ac)
the mark scheme follows the method but why would you do that I don't understand the thought process. Would you always do that if you have a question in this same format. Thanks
Well I assume they'll always give you an iteration formula to prove since there are others you could try. You could say xn+1 = (1/4)exn for instance. If you actually try and use that it just diverges, I think, but still.. it tends to be a matter of "show this" so just rearranging an equation; thus in the context of this exam you shouldn't have to think too much (not that I advocate not thinking ). Or are you saying that you don't understand their way of showing that the given form is possible? If so, it's simply a matter of using what's been given to you; since you're looking at finding a minimum point, you set f'(x) = 0 and rearrange for the given format. And yes, you would do the same in similar questions (although some would be looking for roots rather than turning points, so you would use f(x) = 0 instead).
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3 years ago
#643
Omg makes so much sense now, re read the question looked at the diagram and looked at your explanation. I think I just read the question with a blind eye thank you so much !

(Original post by 13 1 20 8 42)
Well I assume they'll always give you an iteration formula to prove since there are others you could try. You could say xn+1 = (1/4)exn for instance. If you actually try and use that it just diverges, I think, but still.. it tends to be a matter of "show this" so just rearranging an equation; thus in the context of this exam you shouldn't have to think too much (not that I advocate not thinking ). Or are you saying that you don't understand their way of showing that the given form is possible? If so, it's simply a matter of using what's been given to you; since you're looking at finding a minimum point, you set f'(x) = 0 and rearrange for the given format. And yes, you would do the same in similar questions (although some would be looking for roots rather than turning points, so you would use f(x) = 0 instead).
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3 years ago
#644
Can someone explain to me here why on the video he knows that the other angle is -Y, I dont really get that part. I would have just done due to like opposite angles I would have done Z + y = pi

https://www.youtube.com/watch?t=736&v=P3owr0cwZbw, its at like 10:05 in the video thanks
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3 years ago
#645
(Original post by Hudl)
Can someone explain to me here why on the video he knows that the other angle is -Y, I dont really get that part. I would have just done due to like opposite angles I would have done Z + y = pi

https://www.youtube.com/watch?t=736&v=P3owr0cwZbw, its at like 10:05 in the video thanks
I will try to explain. In the triangle in the fourth quadrant the angle is negative (imagine -30 degrees), therefore in the triangle in the second quadrant it will have to be positive, so the angle is -y (--30=30 degrees), this means when you add it up and rearrange you get z+y=pi/2, which makes sense because the angle y will now be negative, and as z is greater than pi/2 (from the graph), you need to subtract a value to end up with pi/2.
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3 years ago
#646
Hey guys, I know everything in C3 except for trigonometry, I have no single bit of information about it, I tried understanding it but I just couldn't, I don't know what to do, I'm panicking right now, can I just solve the pastpapers and follow how Examsolutions do it? Please guys help me.
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3 years ago
#647
(Original post by Joey Hassan)
Hey guys, I know everything in C3 except for trigonometry, I have no single bit of information about it, I tried understanding it but I just couldn't, I don't know what to do, I'm panicking right now, can I just solve the pastpapers and follow how Examsolutions do it? Please guys help me.
Ignoring the fact that you really should have learnt it by now and that it is the largest module in C3, I think you have enough time to get it down before the exam. Watch all of exam solutions videos and do as many past paper Qs as possible. At this time, you don't have the luxury of doing solomons and thousands of worksheets so make sure everything you do is the type of Qs that come up in exams. If I were you I would prioritise the most common sub topics in C3 Trig and go for them first. Don't panic - its not too bad.
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3 years ago
#648
Lol I genuinely think C3 is harder than C4 XD
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3 years ago
#649
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3 years ago
#650
Method 2. Step two on Method 1 is wrong, you can't do ln of each seperate term it has to be of all of it, like you did in Method 2.
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3 years ago
#651
(Original post by randlemcmurphy)
Method 2. Step two on Method 1 is wrong, you can't do ln of each seperate term it has to be of all of it, like you did in Method 2.
Actually step two for method 1 is fine because when you ln(e^2x) you just get 2x. He's just not bothered to show that step. But yeah method 2 is correct.
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3 years ago
#652
(Original post by Guitardude165)
Actually step two for method 1 is fine because when you ln(e^2x) you just get 2x. He's just not bothered to show that step.
Surely you should have done ln(y)=ln(e2x-k2). You can only separate the variables when they are multiplied i.e. if y=e2xk2 then you could have done ln(y)=2x+2ln(k)
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3 years ago
#653
Method 2 is correct I agree with randle you needed to do ln(e^2x - k^2). So method 1 is wrong.
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3 years ago
#654
(Original post by randlemcmurphy)
Surely you should have done ln(y)=ln(e2x-k2). You can only separate the variables when they are multiplied i.e. if y=e2xk2 then you could have done ln(y)=2x+2ln(k)
I'm a bit lost XD.Why would you do lny = ln (e2x - k2) ?
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3 years ago
#655
This is what I would do
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3 years ago
#656
Ah right! Cheers, understood

Posted from TSR Mobile
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3 years ago
#657
(Original post by MPH1997)
Ah right! Cheers, understood

Posted from TSR Mobile
Also don't forget to conclude at the end whenever writing out an inverse function "f-1(x) = blah blah in terms of x" otherwise thats a mark lost
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3 years ago
#658
(Original post by Guitardude165)
I'm a bit lost XD.Why would you do lny = ln (e2x - k2) ?
You shouldn't do Method 1. I just corrected the person's mistake.

(Original post by Guitardude165)
This is what I would do
Yep that is right
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3 years ago
#659
I always have a problem when knowing to add "x = real number" when it comes to giving the domain and range?

When is it added and when not?
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3 years ago
#660
(Original post by Joey Hassan)
Hey guys, I know everything in C3 except for trigonometry, I have no single bit of information about it, I tried understanding it but I just couldn't, I don't know what to do, I'm panicking right now, can I just solve the pastpapers and follow how Examsolutions do it? Please guys help me.
If that's the only chapter you have left then don't worry about it.

Go through the edexcel textbook and do the questions, then try past papers and solomons, they will appear hard at first but all there is to trig is to practise and recognise what to do when.
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