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# Official Edexcel C3 Discussion Thread watch

1. (Original post by uer23)
It tends to be over 60 to get an A. Like 62-64 most of the time, although last year was 67/75.
2. Thanks..
3. if we want to find the min/max value of x how do we find it?! (is there some sort of rule)

e.g Rcos(x+z)
where R= root 160 and z= 18.4

HELPPPP!
4. (Original post by jaz_jaz)
if we want to find the min/max value of x how do we find it?! (is there some sort of rule)

e.g Rcos(x+z)
where R= root 160 and z= 18.4

HELPPPP!
well, you know that on a cos curve the maximum value is at 1 and the minimum value is at -1, right?

The angle at which cos is 1 is 0, therefore:

x+18.4=0 and then solve for x

the angle at which cos is -1 is 180, again

x+18.4=180 and then, solve for x.
5. (Original post by jaz_jaz)
if we want to find the min/max value of x how do we find it?! (is there some sort of rule)

e.g Rcos(x+z)
where R= root 160 and z= 18.4

HELPPPP!
Well the maximum/minimum value cos(x) can be is +1 and -1. So the minimum/maximum value would be +R and -R.
6. THE PAPER IS EASY!rELAX
7. (Original post by Noble.)
Well the maximum/minimum value cos(x) can be is +1 and -1. So the minimum/maximum value would be +R and -R.
she wants the min/max value of x [the smallest positive value x can be, as the exams usually say]
8. Getting quite worried about this exam. Been revising for my resit for Biology last 2 days, done very little C3. As soon as I come home today from the exam I will be revising maths like all afternoon/evening and morning.

Here are some questions I got out of a P2 book. I am not sure what to do with them. Anyone fancy doing them?

1) find values for 0-360 for which:
7cosx+sinx=5
I though about using the RCosx, Rsinx but didnt get the right answer,

2) solve for 0-360
2cos(x+50)=sin(x+40)
Im thinking i should use addition formulaes but then didnt know what to do.

3) solve for 0-pi
3sinx+sinx=sin2x
do i used sin2x=2sinAcosB here? then how do i get just sin?

4) sinx=cos^2x for 0-360

i just dont seem to be able to do trig anymore!

I will probably be on here loads later with lots of questions! xxx
9. Ok thanks and jonathan, just because you find the papers easy, doesn't mean everybody does.
10. can someone help me with question 7 june 2005? its only one mark but I don't get it.
11. all of Q7 or a certain part?
12. (Original post by indie_couture)
Getting quite worried about this exam. Been revising for my resit for Biology last 2 days, done very little C3. As soon as I come home today from the exam I will be revising maths like all afternoon/evening and morning.

Here are some questions I got out of a P2 book. I am not sure what to do with them. Anyone fancy doing them?

1) find values for 0-360 for which:
7cosx+sinx=5
I though about using the RCosx, Rsinx but didnt get the right answer,

2) solve for 0-360
2cos(x+50)=sin(x+40)
Im thinking i should use addition formulaes but then didnt know what to do.

3) solve for 0-pi
3sinx+sinx=sin2x
do i used sin2x=2sinAcosB here? then how do i get just sin?

4) sinx=cos^2x for 0-360

i just dont seem to be able to do trig anymore!

I will probably be on here loads later with lots of questions! xxx
Q1: I used Rsin(x+a) and I got 36.87 and 127
Q2:I'm working on it
Q3: Use the sinP+sinQ= 2sin(P+Q/2)cos(P+Q/2) on the LHS
Q4: change the RHS into terms of sine (using cos2x+sin2x=1)
13. (Original post by Kameo)
can someone help me with question 7 june 2005? its only one mark but I don't get it.
I assume you mean part c

p = 2800ae^0.2t/1 + ae^0.2t x e^-0.2t/e^-0.2t

That should start you off, if unsure just ask.
14. Whoever repped me on here, thank you!

...Do we have to know how to prove cos^2 + sin^2 = 1?

This exam is going to be a disaster!!
15. Haven't come across it in any past papers.
16. What were the examiners thinking while making the June 09 paper? Did they purposely create an easy one? Our exam is gonna be NASTY.
17. (Original post by indie_couture)
1) find values for 0-360 for which:
7cosx+sinx=5
I though about using the RCosx, Rsinx but didnt get the right answer,

2) solve for 0-360
2cos(x+50)=sin(x+40)
Im thinking i should use addition formulaes but then didnt know what to do.

3) solve for 0-pi
3sinx+sinx=sin2x
do i used sin2x=2sinAcosB here? then how do i get just sin?

4) sinx=cos^2x for 0-360
1) Is the answer something like 36.8 and 53.1?

3) Use sin2x=2sinxcosx to get
4sinx = 2sinxcosx

Divide by 2, and put all on one side so it equals 0. Take sinx out and you should have sinx(2-cosx) = 0.
So sinx = 0 or cosx=2 (which is impossible)
So x = 0 or pi.

4) Sub cos^2x for 1-sin^2x and solve as quadratic.

18. can some body help me out with parts B D and E
19. (Original post by unamed)
Q1: I used Rsin(x+a) and I got 36.87 and 127
Yes, me too. But when I try substituting those answers back into the equations, I don't get the answer >_>

How do you prove the cos^2[x] + sin^2[x] = 1 though?

20. (Original post by ishta)

can some body help me out with parts B D and E
What paper is this from?

for b) find x?
Ok, for d) sub the upper and lower boundaries of your x4 value into the original equation.
for e) just find x1, x2, x3 etc and write down what happens. It will probably diverge(?) (not come to a constant number)

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