Mathematics: Post your doubts here!

[iKhaled]

For Q10 did you split the differential equation and use partial fractions ?

yes and i got A= 1/1800 and B = 1/1800 y does the mark scheme says A= 2 and B= 2 :S

 

[PhyZac]

PhyZac

isn't the least value of |z| should be 3√2 why the markscheme is saying 3√2/2 :S:S

its question 8(ii)

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_s11_qp_31.pdf

Yup I got answer like yours, i will look more into it.

 

[iKhaled]

Yup I got answer like yours, i will look more into it.

thank u pls do tell me the answer when u get it

 

[Esme]

yes and i got A= 1/1800 and B = 1/1800 y does the mark scheme says A= 2 and B= 2 :S

Ignore the ms :/
Yeah that's what I got too. Now integrate it just like you would normally do.
After integration you get
1/1800(ln|N|) - 1/1800(ln|1800-N| = t/3600 + c
Use t=0, N=300 to find c
c=1/1800(ln|1/5|)

And then solve it to find N in terms of t

 

[iKhaled]

Ignore the ms :/
Yeah that's what I got too. Now integrate it just like you would normally do.
After integration you get
1/1800(ln|N|) - 1/1800(ln|1800-N| = t/3600 + c
Use t=0, N=300 to find c
c=1/1800(ln|1/5|)

And then solve it to find N in terms of t

yeah thats what i got the first time but when i looked through the mark scheme i saw A= 2 and B=2 then i was :O so is our answers considered correct?

 

[PhyZac]

thank u pls do tell me the answer when u get it

Oh very very sorry, when i read your post, i thought you got 3√2 / 2 and MS got 3√2

Anyway, see, check this sketch and try finding the blue line.

 

[Esme]

yeah thats what i got the first time but when i looked through the mark scheme i saw A= 2 and B=2 then i was :O so is our answers considered correct?

The final answer that I got matches the marking scheme, only the steps in between were different

 

[Esme]

Oh very very sorry, when i read your post, i thought you got 3√2 / 2 and MS got 3√2

Anyway, see, check this sketch and try finding the blue line.

iKhaled this is correct
Use sin(π/4) = z/3 (i.e opp/hyp)
You'll get z=3√2 /2

 

[iKhaled]

Oh very very sorry, when i read your post, i thought you got 3√2 / 2 and MS got 3√2

Anyway, see, check this sketch and try finding the blue line.

thanks that helped a lot!

 

[iKhaled]

iKhaled this is correct
Use sin(π/4) = z/3 (i.e opp/hyp)
You'll get z=3√2 /2

yeah i got it now!

 

[iKhaled]

chemistry and math on the same day both hardest paper..cant beeee arghh!!

 

[iFuz]

A < |z| < B
C < Arg(Z) < D

Minimum and max values for these? what formula to be used?

Secondly, when we are asked to take sq root of a complex number and from result we've to predict other root, do we multiply the root we get by -1? or take its u*?
Thirdly, when question is mixed with polynomials, how to get other root? eg. w12 qp32 ?

 

[PhyZac]

A < |z| < B
C < Arg(Z) < D

Minimum and max values for these? what formula to be used?

Secondly, when we are asked to take sq root of a complex number and from result we've to predict other root, do we multiply the root we get by -1? or take its u*?
Thirdly, when question is mixed with polynomials, how to get other root? eg. w12 qp32 ?

For secondly
take its conjugate.

 

[Esme]

A < |z| < B
C < Arg(Z) < D

Minimum and max values for these? what formula to be used?

Secondly, when we are asked to take sq root of a complex number and from result we've to predict other root, do we multiply the root we get by -1? or take its u*?
Thirdly, when question is mixed with polynomials, how to get other root? eg. w12 qp32 ?

For thirdly:
If you're given one complex root, the other will be it's conjugate.

 

[Esme]

A < |z| < B
C < Arg(Z) < D

Minimum and max values for these? what formula to be used?

Secondly, when we are asked to take sq root of a complex number and from result we've to predict other root, do we multiply the root we get by -1? or take its u*?
Thirdly, when question is mixed with polynomials, how to get other root? eg. w12 qp32 ?

As for your first doubt. There's no specific formula. Depends on the question..

 

[iKhaled]

As for your first doubt. There's no specific formula. Depends on the question..

for the first one u will need 2 things..

1. sketch an argand diagram
2. experience in trig

 

[Anika Raisa]

7(ii) and (iii), of http://papers.xtremepapers.com/CIE/...S Level/Mathematics (9709)/9709_s10_qp_31.pdf

Detail on 7 (ii) i can make out |z-u|<1 will be circle with radius 1 n centre 2,2 but cant make out the other inequality!!!
Please help!

Esme or any1?

 

[Esme]

for the first one u will need 2 things..

1. sketch an argand diagram
2. experience in trig

Yep

 

[Esme]

7(ii) and (iii), of http://papers.xtremepapers.com/CIE/...S Level/Mathematics (9709)/9709_s10_qp_31.pdf

Detail on 7 (ii) i can make out |z-u|<1 will be circle with radius 1 n centre 2,2 but cant make out the other inequality!!!
Please help!

Esme or any1?

Mark the point 1 and then mark another point i
Join these two and make their perpendicular bisector

 

[Esme]

7(ii) and (iii), of http://papers.xtremepapers.com/CIE/...S Level/Mathematics (9709)/9709_s10_qp_31.pdf

Detail on 7 (ii) i can make out |z-u|<1 will be circle with radius 1 n centre 2,2 but cant make out the other inequality!!!
Please help!

Esme or any1?

Mark the point 1 and then mark another point i
Join these two and make their perpendicular bisector

And then shade the area inside your circle and below the perpendicular bisector. i.e. the area closer to the point 1