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Official Edexcel C3 Discussion Thread watch

1. (Original post by Get Cape.Wear Cape.Fly.)
It's in the book?!! Nooooooooooooooooooooooooooooooo oooooooooo! K, back to revision then.
Yeah it's in the book, but one of my teachers said it had been removed since, and so did someone a couple of pages ago.

Not sure where they got that info from then?
2. tanXcos2X = 2cos2X
which way shall I solve this? I could either divide both sides by cos2X to get tanX=2, or I could take 2cos2X from both sides and factorise to get cos2X(tanX-2)=0.

Which is the correct and method and in the exam which one should be used?
3. (Original post by skk90)
tanXcos2X = 2cos2X
which way shall I solve this? I could either divide both sides by cos2X to get tanX=2, or I could take 2cos2X from both sides and factorise to get cos2X(tanX-2)=0.

Which is the correct and method and in the exam which one should be used?
Taking the 2cos2x from both sides then factorising because you would lose solutions I think if you divide cos2x both sides.
4. (Original post by Superman_Jr)
Taking the 2cos2x from both sides then factorising because you would lose solutions I think if you divide cos2x both sides.
Yes, do not divide by 2cos2x otherwise you will lose solution, its jus like having a quadratic, and dividing by x, which we don't do.
5. (Original post by Superman_Jr)
Taking the 2cos2x from both sides then factorising because you would lose solutions I think if you divide cos2x both sides.
Both methods are correct. But u need to remember that when u divide by cos2x u infact do lose solutions. Therefore when u divide by term, put that term =0 and recover the lost solutions. In this case when u divide by cos2x, you have to list solutions for cos2x=0. Hence it's easier to factorise and in most cases safer.
6. guys let's ask Questions to eachother in order to prapre for c3. I'll start off: prove that sin^2+cos^2=1 using the addition formulae.
7. It's a bit of a long shot, but does anyone know what music was playing when Phil Tuffnel was talking about Van Gogh on the One Show just now?

It was piano music... That's all I know about it lol

Any help would be very much appreciated!
8. Could someone explain what x (IS NOT EQUAL TO) (2n+1)pi/2 means - what is n? As the equations use x?
9. (Original post by OrangeStu)
Could someone explain what x (IS NOT EQUAL TO) (2n+1)pi/2 means - what is n? As the equations use x?
n is any number at all, it basically means x is not equal to 3 or 5 etc.
10. another q.....cos (2x + 2π/3) =0.5 0<=x<=π

Im getting different answers to the mark scheme.
11. (Original post by skk90)
another q.....cos (2x + 2π/3) =0.5 0<=x<=π

Im getting different answers to the mark scheme.
how different? What answer did u get? Or are u missing solutions?
12. So who else is having a panic attack?

Those cos (A) - cos (B) things are scaring me. I never learnt any such thing! The syllabus didn't explicitly state that we have to know them, yet those formulae books and C3 student books have identities. Oh well -_-
13. (Original post by Doughboy)
So who else is having a panic attack?

Those cos (A) - cos (B) things are scaring me. I never learnt any such thing! The syllabus didn't explicitly state that we have to know them, yet those formulae books and C3 student books have identities. Oh well -_-
Me. Those cos A/B things are on the formulae sheet...In the textbook, they use P and Q instead.
14. (Original post by gottastudy)
Me. Those cos A/B things are on the formulae sheet...In the textbook, they use P and Q instead.
I just revised the proof of sinA to sinB. Doesn't seem too hard anymore...

15. juts go through the solomon papers to get questions on P-Q things...there are numerous questions on them plus how to prove them

dont worry guys!!
16. Hey guys........ I have a really good plan for tomorrow's exam...... Let's all get A's!!!!!!!!!!
17. How is this:
4sin(2y+6) differentiated, this; 8cos(2y+6) where did the 8 come from?
18. Chain rule- differentiate 2y+6 to get 2.
Multiply the 2 by 4 to get 8.
And of course differentiate sin(2y+6) to -> cos(2y+6)
19. (Original post by uer23)
Generally how high are the grade boundaries for C3 ? I'm just about scraping an A (60 Marks) with the past papers I'm doing, I'm scared it might do me over in the real exam if the grade boundaries are particularly high.
20. (Original post by jaz_jaz)
How is this:
4sin(2y+6) differentiated, this; 8cos(2y+6) where did the 8 come from?
when you differentiate sinf(x), it becomes f'(x)cosx.
Using this principle:
differentiate (2y+6) to give 2, then put it in front of the cos:

4(2)cos(2y+6) = 8cos(2y+6)

make sense?

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Updated: June 14, 2010
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