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# Edexcel Core 3 - 21st June 2016 AM watch

1. (Original post by skyjp)
write 8 as a power of 2 and the root as an indice...

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yay thanks!!!!!!!!!!!!!
2. (Original post by Economistician)
Does anyone know why this method doesn't work?

ln2x + ln(2x^2) + ln(2x^3) = 6
ln2x + 2ln2x + 3ln2x = 6
6ln2x = 6
ln2x = 1
e^ln2x = e^1
2x = e^1
x = (e^1)/2
?
ln(a) + ln(b) = ln(ab), only
3. (Original post by Economistician)
Does anyone know why this method doesn't work?

ln2x + ln(2x^2) + ln(2x^3) = 6
ln2x + 2ln2x + 3ln2x = 6
6ln2x = 6
ln2x = 1
e^ln2x = e^1
2x = e^1
x = (e^1)/2
?
Yep. I would have made the same mistake too . If you think of doing it the other way round (second line of working) if you had 2ln2x (for example the second term) you would need to square the whole of '2x' as the term after ln. That is the only reason you have slipped as far as I can see
4. (Original post by throwaway1234567)
You found it easy?
I'm aiming for a B overall and just got 56% on that paper, completely demoralized now and doubting whether I'll be getting that B .
Ohh noo no way , i was sarcastic, i am aiming for a B aswell but that paper was so bad i'm hoping the paper tomorrow is nothing like that
5. Hey can we be asked to work out things like arctan(-1) and sin[arcos(-0.5))] without a calculator?
6. (Original post by ryanroks1)
Please could someone help with this question?
Spoiler:
Show
You managed to do it yet? I can explain it if not
7. (Original post by KINGYusuf)
But how would I know it's root2?

Am I supposed to trial and error or something

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8. (Original post by Hollie G)
Just a quick last-minute question, how do you know whether to use degrees or radians for iteration questions?
Usually iteration does not involve sin, cos or tan, but if it does, automatically use degrees. Before doing this I would suggest reading through the question and looking for anything like pi because if it wants it in radians it will be specific.
9. (Original post by ryanroks1)
Please could someone help with this question?
Spoiler:
Show

Did it sideways but follow the arrows. use pythagoras in triangle.
10. just got 90% on international paper, ill likely panic tomorrow when edexel puts something weird in :s
11. (Original post by joodaa)
Hey can we be asked to work out things like arctan(-1) and sin[arcos(-0.5))] without a calculator?
if you have a calculator, use it
12. (Original post by WillRose)
just got 90% on international paper, ill likely panic tomorrow when edexel puts something weird in :s
did you do jan 2016?
13. (Original post by ryanroks1)
Please could someone help with this question?
Spoiler:
Show
sina = x
14. (Original post by KINGYusuf)
But how would I know it's root2?

Am I supposed to trial and error or something
That's what I did :s. But I think this is as far as they would go as far as having a surd answer like that. They wouldn't ask you to solve x for x^6 =343 and expect you to know it's root(7).
15. (Original post by WillRose)
just got 90% on international paper, ill likely panic tomorrow when edexel puts something weird in :s
16. (Original post by joodaa)
Hey can we be asked to work out things like arctan(-1) and sin[arcos(-0.5))] without a calculator?
: sin(arccos1/2) using triangles to get an exact answer without a calculator
cosA =-1/2
so sin A = root3 / 2
17. (Original post by joodaa)
Hey can we be asked to work out things like arctan(-1) and sin[arcos(-0.5))] without a calculator?
yep Go check out the relevant videos under the C3 section on examsolutions. I wasn't able to do these types of questions but now I can because of those vids!! They're honestly amazing.
18. What's this about a Jan 2016 paper? Thought the Jan ones stopped?? If anyone has a copy could they please attach it? Thank you
19. I pray for a good test tomorow
20. Hey I just did Jan 2013 paper and worked out two of the questions using methods not mentioned anywhere on the mark scheme (not even alternative), now this has made me worried. I gave myself full marks as a i got the correct answers, but what would an examiner do in this case? I believe my methods are correct, but I'm not sure, and if they are why are they not on the markscheme?

If i post them here can anyone help me, maybe tell me if what I did was wrong?

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