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# P3 Revision topic - 1:15pm 9th June - OCR/Edexcel watch

1. (Original post by tammypotato)
is my method wrong or right
The identities are correct.
2. we dont need the proof for the scalar product do we?(im askin that coz its really detailed in the book)
3. (Original post by tammypotato)
we dont need the proof for the scalar product do we?(im askin that coz its really detailed in the book)
Not the proof, but you do need to know how to do it.
4. I still have some problems with the following ideas

1)Finding gradient at a point on a circles - is this just using implicit differentiation?

2)Sketching curves - best way?
-> b^2 - 4ac <0
-> b^2 - 4ac =0
-> b^2 - 4ac >0

How does the above rule work and what are their possible applications in P3 types questions?
5. (Original post by equili3rium)
I still have some problems with the following ideas

1)Finding gradient at a point on a circles - is this just using implicit differentiation?

2)Sketching curves - best way?
-> b^2 - 4ac <0
-> b^2 - 4ac =0
-> b^2 - 4ac >0

How does the above rule work and what are their possible applications in P3 types questions?
I think I remeber now:

Basically get X in terms of Y, i.e.
Y=f(x)

You should then have a quadratic in some form or other:

Y=ax^2+bx+c
Y=ax^4+bx^2+c etc.

Its called the discriminant, you just bung in the values of a,b and c.

b^2 - 4ac <0 Not too sure.
b^2 - 4ac =0 Use this if the question only says there is one point that intersects, i.e. tangent
b^2 - 4ac >0 Use this if the question says that there is more than one point of intersection, i.e. a line passes through two points, find the points.

Anyway it's P1 stuff and I can't remember it.
6. (Original post by Bhaal85)
I think I remeber now:

Basically get X in terms of Y, i.e.
Y=f(x)

You should then have a quadratic in some form or other:

Y=ax^2+bx+c
Y=ax^4+bx^2+c etc.

Its called the discriminant, you just bung in the values of a,b and c.

b^2 - 4ac <0 Not too sure.
b^2 - 4ac =0 Use this if the question only says there is one point that intersects, i.e. tangent
b^2 - 4ac >0 Use this if the question says that there is more than one point of intersection, i.e. a line passes through two points, find the points.

Anyway it's P1 stuff and I can't remember it.
for b^2 - 4ac <0 the parabola doesn't cut the x-axis and has no Real roots.
7. Hopefully this is the right thread this time...
P3 May 2002 again, question 6:

Curve C has parametric equations
x = 5cost y = -2 + 4sint 0<=t<2pi

Find the coordinates of all the points where C intersects the coordinate axes, giving your answers in surd form where appropriate.

Very confused by this one, I hate trig parametric things!

Thanks for any help guys,

Emma x x x
8. Very good work indeed.

Couple of mistakes stopped and a few wrong ideas

[QUOTE]d/dx of tanx = -lncosx
d/dx of tan^2x = sec^2x

isnt d/dx of tanx = sec^2x
d/dx of tan^2x = 2sec^2 2x
Yes you are indeed correct.

d/dx(tanx) dx = sec²x

don't know about the other one.

You are expected to know this off by heart, its not in the formula booklet.
I know its definitely in my formula booklet. Don't know bout yours :O

isnt the integral of tanx = ln sec x?
Correct again.

Binomial Expansion

(1+ax)^n = 1+nax + n(n-1)/2 *(ax)² + n(n-1)(n-2)/6 * (ax)³

If the constant a, is one then the answer is the same anyways.

Hope this helps.

And good luck to anybody whos taking P3 2moro.
9. Hey guys

I just looked on an Edexcel P3 Examiners report, and last summer you only needed 51/75 to get 80UMS. Compared to needing 66/75 in P1.

That made me feel a lot better. Especially as the June 03 paper isnt as bad as some of the other past papers.

Just thought Id share that with you all!
10. I shall add a vectors section in a few moments.
11. (Original post by Bhaal85)
I shall add a vectors section in a few moments.
... after i spent the whole night trying to make notes grrrr lol
12. (Original post by *dave*)
Hey guys

I just looked on an Edexcel P3 Examiners report, and last summer you only needed 51/75 to get 80UMS. Compared to needing 66/75 in P1.

That made me feel a lot better. Especially as the June 03 paper isnt as bad as some of the other past papers.

Just thought Id share that with you all!
the june 2003 is quite hard in my opinion bt i still like the fact than 68% is an A
13. [QUOTE=Neutrinohunter]Very good work indeed.

Couple of mistakes stopped and a few wrong ideas

d/dx of tanx = -lncosx

Yes you are indeed correct.

d/dx(tanx) dx = sec²x

don't know about the other one.

I know its definitely in my formula booklet. Don't know bout yours :O
d/dx(tanx) dx = sec^2x
INT of tanx = -lncosx +c, I thought I corrected this.

(Original post by Neutrinohunter)
Binomial Expansion

(1+ax)^n = 1+nax + n(n-1)/2 *(ax)² + n(n-1)(n-2)/6 * (ax)³

If the constant a, is one then the answer is the same anyways.

Hope this helps.

And good luck to anybody whos taking P3 2moro.
I kept it simple by simply expressing 'ax' as 'x'.
14. Hopefully this is the right thread this time...
P3 May 2002 again, question 6:

Curve C has parametric equations
x = 5cost y = -2 + 4sint 0<=t<2pi

Find the coordinates of all the points where C intersects the coordinate axes, giving your answers in surd form where appropriate.

Very confused by this one, I hate trig parametric things!

Thanks for any help guys,

Emma x x x
Steps

1) Put both y and x = 0

x = 5cost = 0 therefore cos t = 0

cos t = 0 when t = Pi/2, 3Pi/2

y = -2+4sin t therefore 4sin t = 2, sin t = 1/2

sin t = 1/2 when t = Pi/6, 5Pi/6

2) Find the coordinates at all of those points, this means put the values for t into the other equations

For X, Y t values are Pi/6 5Pi/6

5 * cos pi/6 = 5 * root 3/2 Coordinate: (5root3/2,0)

5 * cos 5pi/6 = 5* -root 3/2 Coordinate (-5roo3/2, 0)

For Y, X t values are Pi/2, 3Pi/2

-2 + 4sin Pi/2 = -2 + (4 * 1) Coordinate (0, 2)

-2 + 4sin 3pi/2= -2 + (4 *-1) Coordinate (0, -6)

Hope this helps
15. it is alot easier to score makes on p1 than on p3
16. (Original post by equili3rium)
it is alot easier to score makes on p1 than on p3
Definitely, I got 68/100 in P1 without trying, then resat it and got 96/100, only to bring my mark up.
17. I just looked on an Edexcel P3 Examiners report, and last summer you only needed 51/75 to get 80UMS. Compared to needing 66/75 in P1.

That made me feel a lot better. Especially as the June 03 paper isnt as bad as some of the other past papers.

Just thought Id share that with you all!
Cool, makes me feel definitely a lot better about 2moro's exam.
18. Thank you! That helped loads!

Emma x x x
19. No Problems

I used to find them quite hard.

Can't believe i only got a B on P1, compared to this P3 it seems increibly easy
20. d/dx(tanx) dx = sec^2x
INT of tanx = -lncosx +c, I thought I corrected this.

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