The Edexcel C4 (21/06/12 - PM) Revision Thread

I think you're making the assumption that the variable x has some kind of direct mapping to t. It may do, but in this case it doesn't. Just because the lower limit for the t integral is less than the upper, it doesn't mean that the same will apply for the x integral. What you've done is fine...it just makes sense. Trying to force 2 < x < 0, makes no sense.

it is 2<x<0 unless u times the cartesian eqn by -1

x = 2(1 - sint^2)

y/2 = sint

x = 2 - 2(y/2)^2

x = 2 - 2(y^2 / 4)

2x = 4 - y^2

y^2 = 4 - 2x

y = (4 - 2x)^1/2

can't square root a negative number therefore:

x < 2 (less than or equal to)

also from 0 < t < pi/2

when t = pi/2, x = 0

therefore the domain = 0 < x < 2 (thats equal to as well for both sides)

thanks i got it now ! another question, review exercise question 77 (the last one) (b) when integrating if I take limits 0 to 2pi, it gives me a negative area. The magnititude is correct. How do i know that I have to take 2pi to 0 instead of 0 to 2pi ?

Did anyone else find the jan12 paper ridiculously easy compared to other papers?

If its a negative area does it not just mean it is under the x-axis?

negetive area means the curve is like a n .. and then you have to make it positive... nomral trapizium cures are 'u' 's

really the last question was hard the 8 marks one?

Damn it you beat me.

I kinda liked it lol.

hi how are u how did u find bio can u help me on this please http://www.examsolutions.co.uk/a-lev...June/paper.php
can someone please help me on question 6)d) they are getting the answer as 1.6479 and i am getting 1.2958 ???

i used integration by parts
i got this when i integrated
(Inx)(x-1)-x+In(x)+c?

I kinda liked it lol.

hi how are u how did u find bio can u help me on this please http://www.examsolutions.co.uk/a-lev...June/paper.php
can someone please help me on question 6)d) they are getting the answer as 1.6479 and i am getting 1.2958 ???

i used integration by parts
i got this when i integrated
(Inx)(x-1)-x+In(x)+c?

Could you explain this to me then?



In part (c), why is the denominator of $\frac{dy}{dx}$ taken instead of the numerator?

Did anyone else find the jan12 paper ridiculously easy compared to other papers?

hey i found it WERIDD!... mmm.. i cant open the link =\