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# Edexcel C3,C4 June 2013 Thread watch

1. (Original post by Story)
Hey guys I know im probably just missing something basic but...

If you you square 1/2sin theta cos theta, how do you get 4/4cos^2theta sin^2theta,

I get the bottom part but not how you get the 4 on top?
Anyone?
2. (Original post by yaboy)
I always simplify my direction vectors to the smallest whole numbers, because for one its make it easier to work with and 2 the markscheme usually right it with it there. As for your values for lambda it wont make a difference at all, when you need to find a certain point on the vector for example you will achieve a different lambda but it will be the right one when considering whether you simplified your direction vector or not. Basically it makes no difference.
thank you, guess I made a mistake then!
3. (Original post by Story)
Anyone?
Well its wrong.
Substituting any value for theta contradicts the 4/4.....expression. Its wrong. From where is this?

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4. (Original post by Story)
Anyone?
Where is this question from?
5. If we had sin(x+pi/3)=1 with the interval being 0<= x <=2pi,
how would the interval change?
6. (Original post by StUdEnTIGCSE)
Well its wrong.
Substituting any value for theta contradicts the 4/4.....expression. Its wrong. From where is this?

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(Original post by Anonymous1717)
Where is this question from?
If you Youtube Core 3 Edexcel June 2012 q)5)...its on Maths247's channel? As he is doing the working out, it may just be a mistake then?

If somebody could explain it to me I would appreciate it!
7. (Original post by nm786)
reciprocate the denominator and times it by the numerator. If the denominator's an integer (a) then multiply numerator by 1/a.
Sorry to be a pain but do you mind giving me an example just so I have it crystal clear?
8. C3 is basically 3sf unless told otherwise right?
9. (Original post by alygirl)
Sorry to be a pain but do you mind giving me an example just so I have it crystal clear?
sure, this is GCSE Maths tbh: 1/2 / 1/4 = 1/2 * 4/1 = 4/2 = 2, 1/2 / 4 = 1/2 * 1/4 = 1/8 (because reciprocal of 4 = 1/4)
10. Don't know if this has been posted before but interesting http://www.edexcel.com/Aboutus/press...acepapers.aspx

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11. (Original post by Story)
If you Youtube Core 3 Edexcel June 2012 q)5)...its on Maths247's channel? As he is doing the working out, it may just be a mistake then?

If somebody could explain it to me I would appreciate it!
There was a 4 in the numerator to begin with, he just multiplies by that 4
12. Just say a questions give y=ln3t, how do you know if the (3t) is in brackets or just the 3 is in brackets as I remember one one question they did not give it brackets what do you assume then? As the answer was dy/dx = ln(3) but it did not give brackets to just the 3? I hope this made some sense.
13. (Original post by Mallika)
If we had sin(x+pi/3)=1 with the interval being 0<= x <=2pi,
how would the interval change?
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
14. (Original post by Max28)
There was a 4 in the numerator to begin with, he just multiplies by that 4
I get it now. How did I miss it?

Just to be clear Its because cosec2theta=1/sin2theta
cosec2theta=1/2sintheta costheta, then you square this to get cosec^2 2theta = 1/4sin^2thetacos^2theta, etc?
15. (Original post by Story)
I get it now. How did I miss it?

Just to be clear Its because cosec2theta=1/sin2theta
cosec2theta=1/2sintheta costheta, then you square this to get cosec^2 2theta = 1/4sin^2thetacos^2theta, etc?
That is correct
16. (Original post by usycool1)
Well, the graph is a translation of the graph for 10 ≤ t ≤ 60 (the graph is "shifted" to the right by 60). So, the the translated graph is f(t - 60).

So the equation is:

T = 5 +

Then play around with it a bit using some rules you know for exponentials and you should get it.

They haven't really equated coefficients.
Thanks!
17. Even though I know the exams tomorrow, I cant be bothered to revise.
18. How can completing the square lead to the range?
For example g(x)=x^2 +2ax+2, the range is g(x) is greater than or equal to 2-a^2. How did they get this from completing the square?

http://www.school-portal.co.uk/Group...urceId=3992025
19. Very best of luck with the C3 exam tomorrow everyone, dont forget it starts at 9.00, not 9.30, i made a mistake thinking my chemistry exam was at 9.30 last week and actually arrived late missed the start, like 10 mins of it. Anyway i was wondering if anyone had any good exam tips/strategy for this c3 exam. On a personal note and not wishing not be immodest at all i got 92 ums in jan c3, but thought i might as well resit it and try and get 100ums(since a* is average 90% ums in c3/c4), my revision strategy has been just doing solomon papers, infact the last edexcel paper i did was in january!, i have been getting around 90% on these solomon papers. i really would love to get an A* in maths, C4 is harder than C3 so anyone any tips.
20. (Original post by Anonymous1717)
How can completing the square lead to the range?
For example g(x)=x^2 +2ax+2, the range is g(x) is greater than or equal to 2-a^2. How did they get this from completing the square?

http://www.school-portal.co.uk/Group...urceId=3992025
The range represents what the y-values go between. g(x) is a positive quadratic, so it has a minimum. By completing the square, you find the coordinates of that minimum, therefore telling you what g(x) has to be greater than or equal to

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