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Edexcel A2 C3 Mathematics 12th June 2015

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Original post by Emmi12345
photo-2.jpg

There you go. :biggrin: Die no more.


thanks
http://www.thestudentroom.co.uk/showthread.php?t=3399451
Original post by Bealzibub
Yeh .. i messed up on it too.

It was 5 marks aswell.

Then my mind went blank on part b of that question and there goes 9 marks.

Rest was pretty good though. Porbably lost 12-13 marks


He didn't 'mess up' on it... He's a Maths teacher (I think?). He just didn't sit the paper so he wants to see this trig identity to see why everyone found it so hard :biggrin:
Don't worry about it though, I think quite a few people didn't get it...
C3 was difficult
Original post by TeeEm
I am dying to see this trig identity ...


Trig identity: how i did it...
split thing into 1/cos2x + sin2x/cos2x
then make common denominator of cos2x so it is (1+sin2x)/cos2x
then expand the double angle formulae so (1+2sinxcosx)/(cosx)^2 -(sinx)^2
then factorise denominator (diff of 2 squares) so
(1+2sinxcosx)/(cosx + sinx)(cosx - sinx)
using identity (sinx)^2 + (cos)^2 =1, sub in the sin and cos parts so you get
((sinx)^2 +(cosx)^2) +2sinxcosx)) / (cosx + sinx)(cosx - sinx)
the numerator can be factorised to (cosx+sinx)(cosx +sinx),
so now u have (cosx+sinx)(cosx +sinx) / (cosx + sinx)(cosx - sinx)
and then one of the (cosx + sinx) brackets cancel with the one on the bottom leaving u with (cosx + sinx) / (cosx -sinx)
sorry for it being hard to read...
the equation of the asymptote for the first graph was y=-5, was there an asymptote for the second graph? If so what was the equation.
Original post by thatNoseyParker
Just another copycat troll, sad really..:h:


suck out they aren't trolling they are just smarter than you....
Original post by Johann von Gauss
Prove: sec 2x + tan 2x = (cos x + sin x) / (cos x - sin x)

Spoiler



thanks
Theres a C3 difficulty poll on this link btw

http://www.thestudentroom.co.uk/showthread.php?p=56920399&highlight=core%203
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Original post by hanif ahmed
there was 10...on the last page after the division question


*sarcasm*
Original post by ColeNate
9 for regular C3. Last question involved fractions, quadratics and k.


****
Original post by PaulCJH
My Answers:
1. 2p/(1-p^2), 1/((p^2+1)^1/2), (1+p)/(p-1)
2. x> or equal to ln5/2, Solutions: ln3/2, ln7/2.
3. 26.57, 2 root 5, 51.8 and -25.3, k<2 root 5 and k>2 root 5
4. 20, ln2/40, 93
5. 4pi^2, 1/3pi
7. -4e^-4<g(x)<1/(8e)
8. 2.820, 5.962,
9. increasing, -3k/(x-2k)^2

Some might be wrong please bear that in mind.


For question 3, you're meant to put k>2root5 and k<-2root5 right?
Reply 3072
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Qass22
Guys, can i see a method for 5 b) please? The tangent to the curve question! Much appreciated.
Original post by candol
Didn't do paper, but if i understood question correct you need to multiply top and bottom by cosx + sinx . Then simplify and use double angle formula to get sin2x/cos2x = 1/2 which is tan2x=1/2 etc

Hi, I also had a brain freeze but I got it as 3cosx +sinx and put it in Rcos(x+a) form- I know I got thr right answers but will I still get the marks for not using tan?
How did you find this paper? Vote Nowhttp://strawpoll.me/4609429/r
How many marks for 96UMS roughly?
Me too 😭
Nearly cried when i found out
Original post by dominicwild
How did you get it to be increasing?

K was negative and it was divided by the square of some function of x. Meaning the gradient at any point could only be negative. As it's always going to be negative/positive = negative. Meaning it's a decreasing function?


The number kept on getting smaller, and it was a negative, so a negative number getting smaller means that its an increasing function, because the value of it is actually increasing.
Original post by Bustamove
I have nothing against people saying that they did well, but making fun of others not doing as well as you is not something that I agree with...


Oh yeah I agree we shouldn't belittle people who did hard, that's a general rule. I personally haven't belittled people who found it hard, I was just trying to put a neutral perspective on things.
The y=2e^x-5 graph question, was it assymptote at y=-5 and (0,-3) and then part b, y=5 and (3,0) ??? And then they intersect at ln(5/2)
and last part - two solutions - x=ln(7/2) and ln(3/2)
??????????????????????????!!!!!!

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