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# Edexcel Maths C3 watch

1. (Original post by !"£\$%)
how likely are trig equations with arcsin/ arccos?? I pretty much have no idea when they come up...
From looking at the past papers they are quite unlikely, what dont you understand about them?
give an example and lets see if we can help!
2. I've done all the past papers but I'm too scared to do the solomon papers, because I'll just fail them so badly and be depressed all night.
3. (Original post by chaz1992)
2 (sec^2 (c))^1/2 = 2 sec (c)

LoL. Just got what it said!

dy/dx:

2 sec (c) tan (c)

I'm on it this week. Last week I was struggling with C3, now i'm getting everything right. Done loads of past papers and my worst score was 72/75 in Jan 2007.

Anyone know when the hardest C3 paper was set?
Jan 2010 for sure. Well done on your marks.
4. I'm getting 65-70% on past papers which is good enough but would be nice to get a bit higher just incase.

I'm solid at most sections except for the trigonometry. Does anyone have any tips on things to remember which would help me? Thanks alot
5. (Original post by jamz0770)
I'm getting 65-70% on past papers which is good enough but would be nice to get a bit higher just incase.

I'm solid at most sections except for the trigonometry. Does anyone have any tips on things to remember which would help me? Thanks alot
Most of the trig questions come in parts and so the best tip is try and use part a in part b or c wherever possible! other that that trig is just about knowing the identities and being careful with the range when using cast.
6. I'm doing it tomorrow, not sure how I feel about it cause only started revising on Friday lol. damn
7. (Original post by mouldy)
Most of the trig questions come in parts and so the best tip is try and use part a in part b or c wherever possible! other that that trig is just about knowing the identities and being careful with the range when using cast.
Okay thanks, Any Identities that are better to know than others?

Okay what do you mean by that with Cast? (I understand what Cast is but what do you mean be careful with the range?)
8. (Original post by FZka)
I'm taking it for the first time tomorrow & it feels horrible.. I don't know what to expect.
Expect the worse. That's all I'm saying...
9. (Original post by jamz0770)
Okay thanks, Any Identities that are better to know than others?

Okay what do you mean by that with Cast? (I understand what Cast is but what do you mean be careful with the range?)
if you know the sin^2x + cos^2x = 1 you can work out the cot^2x etc from them and then you can also use that identity to work out the cos2A identities etc from the cos(A+B) formula you are given

nifty trick

also a good trick for the differentiating/integrating of trig functions:

sinx
|
-cosx ---- cosx
|
-sinx

go clockwise for differentiating and anti clockwise for integrating
edit: it's supposed to be a cross by the way...
10. Do you think the paper will be harder because of the new A* grade and stuff? Or do you think Jan 2010 was an exception
11. (Original post by jamz0770)
Okay thanks, Any Identities that are better to know than others?

Okay what do you mean by that with Cast? (I understand what Cast is but what do you mean be careful with the range?)
See my earlier post with reference with other identities.

And with the range what i mean is if your equation is 2cos2x=1 0<x<360
then be careful to change it too 0<2x<720 to ensure you get all the correct answers
12. (Original post by fionaflowers)
if you know the sin^2x + cos^2x = 1 you can work out the cot^2x etc from them and then you can also use that identity to work out the cos2A identities etc from the cos(A+B) formula you are given

nifty trick

also a good trick for the differentiating/integrating of trig functions:

sinx
|
-cosx ---- cosx
|
-sinx

go clockwise for differentiating and anti clockwise for integrating
edit: it's supposed to be a cross by the way...
Okay thanks, Erm could you explain the first bit?

I know that Cos^2x + Sin^2x = 1 but how does that tie in with the other bits you said?

and for some reason I know that when differentiating it goes Sin>Cos>-Sin>-Cos>Sin, No idea why I know that but I do
13. oh, and i will probably die on friday in the C4 exam

integration is the bane of my life
14. (Original post by andrew.P)
hopefully not the graphs for arcsinx, arccosx, arctanx.. cba to learn them, have they come up in exams before?
arcsin has definitely come up before, quite unusual though.

Just draw the graph of the trig function.

Rotate 90 clockwise

Flip vertically

Pretty easy.
15. pahah i got an impressive 43
but ive been revising since early april, done all the past papers nearly twice.
so i should be able to get a B
really hope my heard work pays off, really nervous! going to be so gutted if months of revision doesnt help me out!
im feeling more confident, but i just feel theres more pressure this time as its my last time to take it, so its making me more nervous
16. (Original post by jamz0770)
Okay thanks, Erm could you explain the first bit?

I know that Cos^2x + Sin^2x = 1 but how does that tie in with the other bits you said?

and for some reason I know that when differentiating it goes Sin>Cos>-Sin>-Cos>Sin, No idea why I know that but I do
with that identity, if you divide it by sin^2x you will get cot^2x and cosec^2x and if you divide it by cos^2x you will get tan^2x and sec^2x

with the compound angles, if you let a=b in e.g cos(A+B)
you'll get cos2x = cos^2x - sin^2x
then you can rearrange the cos^2x + sin^2x = 1 identity to get the other indentities for cos2x
i hope this makes sense
17. learn how to go from sin^2 + cos^2 = 1 to the identities fot cot^2 and tan^2. They are on every paper.

Don't forget you multiply all the angles by a factor in the double angle formula to give a formula for sin4x; sin0.5x; sin3x etc
18. (Original post by jamz0770)
Okay thanks, Erm could you explain the first bit?

I know that Cos^2x + Sin^2x = 1 but how does that tie in with the other bits you said?

and for some reason I know that when differentiating it goes Sin>Cos>-Sin>-Cos>Sin, No idea why I know that but I do
If you divide by sin^2x then you get (sin^2x)/(sin^2x)+(cos^2x)/(sin^2x)=1/(sin^2x) which equals 1+cot^2x=cosec^2x
the other forumla is found by doing the same but dividing by cos^2x!
19. learn how to go from sin^2 + cos^2 = 1 to the identities fot cot^2 and tan^2. They are on every paper.

Don't forget you multiply all the angles by a factor in the double angle formula to give a formula for sin4x; sin0.5x; sin3x etc
20. My school doesn't allow Jan maths exams, so this is my first attempt. I'm going to fail so hard

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