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# The Edexcel C3 (14/06/12 - AM) Revision Thread Tweet

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IMPORTANT: You must wait until midnight (morning exams)/4.30AM (afternoon exams) to discuss Edexcel exams and until 1pm/6pm the following day for STEP and IB exams. Please read before posting, including for rules for practical and oral exams. 28-04-2013
1. Re: The Edexcel C3 (14/06/12 - AM) Revision Thread
(Original post by StraightUpG)
Find in terms of pi, the solutions of the equation:

Sin(5X) + Sin(X) =0

for the x interval, 0<=(X)<pi

This is straight off a Solomon paper, and was wondering if a question like this can come up in an edexcel paper for C3 as I havent seen a question like it in any past papers.

Think about the for trigonometric identity:

sin A + sin B = 2 sin [(0.5)A + B] cos [(0.5)A − B]

Where A = 5x AND B = x

Hope that Helps!
Last edited by Amy-Chod; 31-05-2012 at 21:03. Reason: Oops typo! Sorry!
2. Re: The Edexcel C3 (14/06/12 - AM) Revision Thread
For proof questions in C3 and C4 etc. If you can't show that X=Y can you do the reverse and show that Y=X.
Will you get marked down? I mean its still showing that one form is identical to the other. I am just asking because sometimes when i do past papers involving proof i get mindblocked and just do the reverse of what they are telling me.
3. Re: The Edexcel C3 (14/06/12 - AM) Revision Thread
Need to do well in C3. Got a B in January.
4. Re: The Edexcel C3 (14/06/12 - AM) Revision Thread
(Original post by jlnbello)
For proof questions in C3 and C4 etc. If you can't show that X=Y can you do the reverse and show that Y=X.
Will you get marked down? I mean its still showing that one form is identical to the other. I am just asking because sometimes when i do past papers involving proof i get mindblocked and just do the reverse of what they are telling me.
That's fine, as long as you can show that one side equals the other side then you have proven it.

Generally, you use the side that looks the most diffucult to prove the other side.
5. Re: The Edexcel C3 (14/06/12 - AM) Revision Thread
(Original post by NutterFrutter)
That's fine, as long as you can show that one side equals the other side then you have proven it.

Generally, you use the side that looks the most diffucult to prove the other side.
phew thanks man
6. Re: The Edexcel C3 (14/06/12 - AM) Revision Thread
Anyone here resitting from Jan ?
7. Re: The Edexcel C3 (14/06/12 - AM) Revision Thread
(Original post by Eternal*)
Anyone here resitting from Jan ?
Yup.
8. Re: The Edexcel C3 (14/06/12 - AM) Revision Thread
do you guys think this would be easier or harder paper ?
9. Re: The Edexcel C3 (14/06/12 - AM) Revision Thread
(Original post by otrivine)
do you guys think this would be easier or harder paper ?
I think it will be slightly more difficult than the January paper as that had higher than normal grade boundaries.
10. Re: The Edexcel C3 (14/06/12 - AM) Revision Thread
(Original post by NutterFrutter)
I think it will be slightly more difficult than the January paper as that had higher than normal grade boundaries.
like cause this is my first time taking c3 ! i mean like how much harder can they make it cause i looked at like previous past papers the questions look similar just different numbers>?
11. Re: The Edexcel C3 (14/06/12 - AM) Revision Thread
(Original post by NutterFrutter)
Yup.

(Original post by otrivine)
do you guys think this would be easier or harder paper ?
Harder, because there are more people doing it...

Why have I got negged??????
Last edited by Eternal*; 29-05-2012 at 16:32.
12. Re: The Edexcel C3 (14/06/12 - AM) Revision Thread
(Original post by StraightUpG)
Find in terms of pi, the solutions of the equation:

Sin(5X) + Sin(X) =0

for the x interval, 0<=(X)<pi

This is straight off a Solomon paper, and was wondering if a question like this can come up in an edexcel paper for C3 as I havent seen a question like it in any past papers.
Solomon papers have a repuatation for being a lot above the standard of edexcel papers. I think it would be very unlikely for you to get a question like this in your paper, but just in case:

Let A = 5X and B = X

Sin(A) +Sin (B) = 0

Sin A + Sin B = 2 Sin((A + B)/2) Cos((A − B)/2) = 0 This is in the Core 3 formula booklet, which you will be given in the exam.)

Substituting X and 5X back in:

2 Sin((5X + X)/2) Cos((5X - X)/2) = 0

2 Sin (3X) Cos (2X)=0

Sin (3X) Cos (2X)=0

Therefore:

EITHER Sin(3X) = 0

X = pi/3 or 2pi/3 (0 and pi excluded because they are JUST outside the range.)

OR Cos(2X) = 0

X = pi/4 or 3pi/4

Therefore:

the solutions of the equation

Sin(5X) + Sin(X) =0

for the x interval, 0< X <pi are

X = pi/4, pi/3, 2pi/3, and 3pi/4

I hope this helps
13. Re: The Edexcel C3 (14/06/12 - AM) Revision Thread
(Original post by Amy-Chod)
Think about the for trigonometric identity:

sin A + sin B = 2 sin [(0.5)A + B] sin [(0.5)A − B]

Where A = 5x AND B = x

Hope that Helps!
This isn't correct

sin A + sin B = 2 sin [(0.5)A + B] COS [(0.5)A − B]
,not 2 sin [(0.5)A + B] SIN [(0.5)A − B]

By the way, this formula is on the Edexcel formula booklet, which you will be given in the exam, so you will NOT need to learn this, don't worry!
Last edited by hippogriff; 29-05-2012 at 21:08.
14. Re: The Edexcel C3 (14/06/12 - AM) Revision Thread
june 06 paper is a b***h lol the rest of the papers are ok except that paper
15. Re: The Edexcel C3 (14/06/12 - AM) Revision Thread
(Original post by Lindizya)
june 06 paper is a b***h lol the rest of the papers are ok except that paper
I didn't like question 7 at all, the rest were fine though.
16. Re: The Edexcel C3 (14/06/12 - AM) Revision Thread
Guys what are the half angle identities?
17. Re: The Edexcel C3 (14/06/12 - AM) Revision Thread
18. Re: The Edexcel C3 (14/06/12 - AM) Revision Thread
any one else thinks C3 is actually a lot easier once you have done c4?
19. Re: The Edexcel C3 (14/06/12 - AM) Revision Thread
(Original post by arnab)
any one else thinks C3 is actually a lot easier once you have done c4?
It definitely is! especially when it comes to differentiation and fractions!
20. Re: The Edexcel C3 (14/06/12 - AM) Revision Thread
(Original post by arnab)
any one else thinks C3 is actually a lot easier once you have done c4?

(Original post by 0range)
It definitely is! especially when it comes to differentiation and fractions!
Agreed!
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