# Edexcel A2 C3 Mathematics 12th June 2015Watch

This discussion is closed.
3 years ago
#681
(Original post by randlemcmurphy)
Are you planning on remembering identities such as:
cos(x)=sin(90-x)
sin(x)=cos(90-x)
sin(-x)=-sin(x)
cos(-x)=cos(x)
(The bottom two are rather easy to remember)
These are obvious if you know your graphs, learn the graphs not these!
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3 years ago
#682
As the domain of t is 0 to 12. The way the sine graph is your next solution would be like 14 hours. Look at this but it's hard to explain on here! https://07a69ccf283966549a9350d1a669...%20Edexcel.pdf
I understand now. I forgot that the domain of t alone is 0 < t < 12, therefore the domain of 4(pi)(t) is 0 < 4(pi)(t) < (48/25)(pi)(t), which is 6.031.
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3 years ago
#683

Can someone help me with part c?

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3 years ago
#684

Why does my way only give one of the solutions?

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3 years ago
#685
(Original post by Medicjug)

Can someone help me with part c?

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Don't you just sub in T=18 k=0.0124 and t=70 then find B
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3 years ago
#686
(Original post by studentwiz)
Don't you just sub in T=18 k=0.0124 and t=70 then find B
I tried that it turns out you need to sub in t-60

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3 years ago
#687
Guys when you have -3sinx=cosx
How can we divide by cosx and do tanx=-1/3

I thought you can't divide by trig functions cause you lose the values where they equal 0????

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3 years ago
#688
(Original post by Medicjug)
Guys when you have -3sinx=cosx
How can we divide by cosx and do tanx=-1/3

I thought you can't divide by trig functions cause you lose the values where they equal 0????

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This is only a problem when you would be dividing by zero. Cos and sin cannot both be zero for the same value of x so this isn't an issue here.
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3 years ago
#689
(Original post by Medicjug)
Guys when you have -3sinx=cosx
How can we divide by cosx and do tanx=-1/3

I thought you can't divide by trig functions cause you lose the values where they equal 0????

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What does the actual question say? I suspect x=/=0 is in there somewhere

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3 years ago
#690
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3 years ago
#691
(Original post by cerlohee)
Hi everyone, so I'm having trouble with this question: http://i.gyazo.com/90da8d80d402473cdbbd213855aedf55.png
I have worked out that b is 6, how do I then go onto work out A? Thanks

ALSO this question: http://i.gyazo.com/893eaaf9bd27c4b0a02a8512344a0a6c.png
I got a max value of 1.107 by making 100sinsq(theta-1.107)=0??
Anyone??:3
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3 years ago
#692
(Original post by Medicjug)
I tried that it turns out you need to sub in t-60

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Yeah it's (t-60) because the graph translates from 10 -> 70 and 60 -> 120

If you notice it's a difference of 60 so you write it as 10 < t-60 < 60

Please note: You DONT write it as t+60 which most people would automatically assume because if you look at my boundaries and rearrange it, doing t+60 would give -50 < t < 0
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3 years ago
#693
which would you guys say are the hardest c3 papers that have come out so far (except last years) ive basically done all of the gold papers, now looking to fit in a few of the actual papers, which ones are worthwhile doing?
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3 years ago
#694
(Original post by s.c.a1)
which would you guys say are the hardest c3 papers that have come out so far (except last years) ive basically done all of the gold papers, now looking to fit in a few of the actual papers, which ones are worthwhile doing?
Well in 2013 100 ums was like 64

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3 years ago
#695
(Original post by s.c.a1)
which would you guys say are the hardest c3 papers that have come out so far (except last years) ive basically done all of the gold papers, now looking to fit in a few of the actual papers, which ones are worthwhile doing?
June 2013 is the notorious one. Otherwise take your pick from any after 2013 including IAL and R papers

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3 years ago
#696
Anyone know a quick way of remembering all the identities? :]
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3 years ago
#697
(Original post by pearl_rose)
Anyone know a quick way of remembering all the identities? :]
Firstly you don't really need to know a whole lot, as most are either on the formula sheet or can easily be derived from it eg sin2a isn't on there but sin(a+b) is so you can just do sin(a+a) to get the identity for sin2a. The only ones you really have to know are 1+tan^2 =sec^2 and 1+cot^2 =cosec^2

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3 years ago
#698
(Original post by pearl_rose)
Anyone know a quick way of remembering all the identities? :]
(Original post by samb1234)
Firstly you don't really need to know a whole lot, as most are either on the formula sheet or can easily be derived from it eg sin2a isn't on there but sin(a+b) is so you can just do sin(a+a) to get the identity for sin2a. The only ones you really have to know are 1+tan^2 =sec^2 and 1+cot^2 =cosec^2

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For "1+tan^2 =sec^2 and 1+cot^2 =cosec^2" I would just recommend remembering sin2x+cos2x=1, and then altering that in the exam for the specific identity needed.
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3 years ago
#699
(Original post by randlemcmurphy)
For "1+tan^2 =sec^2 and 1+cot^2 =cosec^2" I would just recommend remembering sin2x+cos2x=1, and then altering that in the exam for the specific identity needed.
Yes it is fairly easy to derive that one as well (just divide by sin^2 or cos^2) I just put that one as a lot of people don't realise that there is even an identity linking them so may not realise to do that in the exam

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1
3 years ago
#700
Can someone help me on question 5)b) ?
I don't understand how you can find the lower limit? help?
is it a recirpocal? and what is the best way to work out the range?
I usually draw a table but it takes too long

http://qualifications.pearson.com/co...-June-2014.pdf

Heres the markscheme
http://qualifications.pearson.com/co...-June-2014.pdf
Thanks
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