Edexcel C3,C4 June 2013 Thread

Reply 2840

HARDZ994

1

WOOP. DO All Trig And Differentiation Questions For All Past Papers From Jan 2005 to Jan 2013. RIP ME.

Reply 2841

Spellstheend

what do we need to know about half angles? i havent come across it really?

Reply 2842

Zaphod77

1

Original post by Story

Hey, if you used the method of drawing the graph out and do tan^-1(-1) you get 45, but the corresponding x value -45 is in the middle of 90 and 180, do we just assume and either add 90+45 or minus 180-45?

Sorry, I'm a bit confused with the question. If you do arctan(-1) you get -45 degrees. Using the graph, tan(x) crosses the x axis when x=0, so for 0 degrees you're at 0. The next time you get 0 is at 180 degrees on the graph, as it recurring.-45 degrees is 45 below 0, so you have to take away 45 from the 180. Make any sense? I swear I word things in the weirdest of ways sometimes...

Reply 2843

BenNiB

Original post by nm786

no problem, yeah that's the only paper i've seen it come up. I got a feeling they will ask us this stuff tomorrow.

Got that feeling too but then I thought considering they lost the paper that changes matters. Can't imagine the replacement paper will have it in.. or maybe it could? It's silly to try and second guess the examiners I guess but I cant help myself ahah

Reply 2844

Scorcher

1

I've been getting 70+ in every C3 paper I've been doing, just done Jan 07 and got 57/75. Really struggled with that paper and it's done wonders to my confidence with 17 hours to go until the exam :frown:

(edited 10 years ago)

Reply 2845

Zaphod77

1

Original post by Spellstheend

what do we need to know about half angles? i havent come across it really?

Basically, the half-angle formulae are the same as the double angle formulae, except instead of theta you have 1/2 theta, and instead of 2 theta you have theta. As it's just the same as double angle formulae, if you can do one, you can do the other :smile:

Reply 2846

Spellstheend

Original post by Zaphod77

Basically, the half-angle formulae are the same as the double angle formulae, except instead of theta you have 1/2 theta, and instead of 2 theta you have theta. As it's just the same as double angle formulae, if you can do one, you can do the other :smile:

ok cheers

didnt fancy finding something I had no clue about this close to the exam!

Reply 2847

nm786

2

Original post by BenNiB

Got that feeling too but then I thought considering they lost the paper that changes matters. Can't imagine the replacement paper will have it in.. or maybe it could? It's silly to try and second guess the examiners I guess but I cant help myself ahah

You never know man anything's possible with Edexcel. :biggrin:

Reply 2848

SortYourLife

16

Original post by masryboy94

could no one post or talk about the c3 exam on this forum after tomorrow's exam, some people (like me) will prefer not to talk about it yet want to use this forum to discuss c4 ... Thank you all and hope no one takes offence to this !

Why isn't there a separate thread for c4 ? :s

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Reply 2849

Amila888

anybody did Chemistry today? Hope C3 will be nothing much different from what we'r used to see in pastpapers. :colondollar:

Reply 2850

bestfriends33

1

From the june 2010 paper.. http://www.edexcel.com/migrationdocuments/QP%20GCE%20Curriculum%202000/june2010-qp/6665_01_que_20100615.pdf
Question 7d..
I keep getting 2.098855812 and not 2.096. The other value for 6.711 is fine.
Can someone please help me? And also how to finish the question off by getting the times 14:06, 18:43?
Thank you so much in advance! :smile:

Reply 2851

Story

Original post by Zaphod77

Sorry, I'm a bit confused with the question. If you do arctan(-1) you get -45 degrees. Using the graph, tan(x) crosses the x axis when x=0, so for 0 degrees you're at 0. The next time you get 0 is at 180 degrees on the graph, as it recurring.-45 degrees is 45 below 0, so you have to take away 45 from the 180. Make any sense? I swear I word things in the weirdest of ways sometimes...

I think I get it, So you do 180-45, to get 135, Its a bit easier to understand for sin and cos graphs, but yeah is that how you do it then?

Also, a lot of people use the quadrant method is it cool if you draw it out and work it out that way?

Reply 2852

orange94

How do you find the range? I usually sub in the x value into the equation to find it. Sometimes it doesn't work

HELP!!!!!!

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Reply 2853

Zaphod77

1

Original post by Story

I think I get it, So you do 180-45, to get 135, Its a bit easier to understand for sin and cos graphs, but yeah is that how you do it then?

Also, a lot of people use the quadrant method is it cool if you draw it out and work it out that way?

I'll be honest, I've always used the quadrant way :tongue:

You must make sure you know the shapes of the graphs, but it doesn't matter which method you use so long as you get the right answer :smile:

And yeah, basically, you just have to consider the shape of the graph and where it's the same, as it's still recurring :smile:

Reply 2854

Mallika

15

Original post by yaboy

it wouldn't

some people choose to write the interval as pi/3<x<7pi/3 before they take away their pi/3 to the answers but i just think thats a hassle

That's what I do :tongue:

Thank you!

Reply 2855

JenniS

2

Original post by nm786

Yup, jan 2007 8ii.

how do you do that question?

Reply 2856

Westeros

12

Can someone help me with this question from C3 June 2005 please:

f(x) =

3e^x -

\frac{1}{2}

\ln x

-2

f'(x) =

3e^x -

\frac{1}{2x}

The curve with equation y=f(x) has a turning point P. The x-coordinate of P is alpha (

\alpha

).

Show that

\alpha =

\frac{1}{6}

e^{-\alpha}

Thanks :-)

Reply 2857

Scorcher

1

Original post by Westeros

Can someone help me with this question from C3 June 2005 please:

f(x) =

3e^x -

\frac{1}{2}

\ln x

-2

f'(x) =

3e^x -

\frac{1}{2x}

The curve with equation y=f(x) has a turning point P. The x-coordinate of P is alpha (

\alpha

).

Show that

\alpha =

\frac{1}{6}

e^{-\alpha}

Thanks :-)

Let me know if you don't understand the method and I will try to explain further.

photo (2).JPG

Reply 2858

Westeros

12

Original post by bestfriends33

From the june 2010 paper.. http://www.edexcel.com/migrationdocuments/QP%20GCE%20Curriculum%202000/june2010-qp/6665_01_que_20100615.pdf
Question 7d..
I keep getting 2.098855812 and not 2.096. The other value for 6.711 is fine.
Can someone please help me? And also how to finish the question off by getting the times 14:06, 18:43?
Thank you so much in advance! :smile:

When I was working this out, I also got 2.0988... etc, the mark scheme actually says 'Either awrt 2.1 or awrt 6.7', so that's still the correct answer when you round!

To get the final answers, this part is quite easy when you find out what you have to do! so now you have 2 times, 2.0988 and 6.711... etc, each of these mean 2 hours and ____ minutes, or for the other value, 6 hours and ____ minutes, however we need to convert them into minutes since they are currently in hours.

So for t=2.0988
We take the 0.0988 and multiply it by 60 which gives 5.928 minutes
Add that onto the 2 hours (on a 24 hour clock), we get 14:06

And for t=6.71136...
Take the 0.71136, multiply it by 60 to get the minutes = 42.68.. mins
Add that onto the 6 hours, and we get 18:43 when rounded

Hope this helped :biggrin:

(edited 10 years ago)

Reply 2859