Author Topic: Maths/Physics help  (Read 23501 times)

Offline astarmathsandphysics

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Re: Maths/Physics help
« Reply #75 on: April 10, 2009, 10:42:30 pm »
That is what I did to get two integrals.

Offline omarsubei

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Re: Maths/Physics help
« Reply #76 on: April 10, 2009, 10:47:09 pm »
Ya I looked at that. I don't understand their method, but I can see that in your method, you put the same equation twice, you need to put one of them as +square root... and the other as -square root..., if you see what I mean

Offline omarsubei

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Re: Maths/Physics help
« Reply #77 on: April 10, 2009, 10:50:19 pm »
I don' get how you went from step one to two, how'd you put the integrals together?

Offline astarmathsandphysics

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Re: Maths/Physics help
« Reply #78 on: April 10, 2009, 10:51:49 pm »
You are right. I corrected my mistake.

Offline astarmathsandphysics

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Re: Maths/Physics help
« Reply #79 on: April 10, 2009, 10:55:03 pm »
I don' get how you went from step one to two, how'd you put the integrals together?

Exapnad the brackets and simplify. You can just add the integrands. The squared terms cancel and for one term I get--=+

Offline radam

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Re: Maths/Physics help
« Reply #80 on: April 23, 2009, 01:11:11 pm »
Hey;

I'd appreciate some help with this question;

(from the previous subsection b is an imaginary root of the equation z^5-1=0 and b^4+b^3+b^2+b+1=0)
________________________________________
Q 13, PART B, MATH HL NOV 08

c) If u=b+b^4 and v= b^2+b^3, show that

i) u+v=uv=-1
ii) u-v= sqrt(5) , given that u-v>0
_______________________________________

for i) Proving that u+v=-1 is not difficult... but i have no idea how to prove that uv=-1, or for ii) how u-v is sqrt(5).

Help would be greatly appreciated :)

Offline astarmathsandphysics

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Re: Maths/Physics help
« Reply #81 on: April 23, 2009, 01:53:03 pm »
Hey;

I'd appreciate some help with this question;

(from the previous subsection b is an imaginary root of the equation z^5-1=0 and b^4+b^3+b^2+b+1=0)
________________________________________
Q 13, PART B, MATH HL NOV 08

c) If u=b+b^4 and v= b^2+b^3, show that

i) u+v=uv=-1
ii) u-v= sqrt(5) , given that u-v>0


_______________________________________

for i) Proving that u+v=-1 is not difficult... but i have no idea how to prove that uv=-1, or for ii) how u-v is sqrt(5).

Help would be greatly appreciated :)

i)uv=(b+b^4)(b^2+b^3)=b^3+b^4+b^6+b^7 now use b^5=1 ie B^6=b and B^7=b^2 so we have b^3+b^4+b +b^2=-1 too.

I will answer the second part as soon as I come back, but I have to go RIGHT NOW and teach some maths.

ii)(u-v)^2=u^2-2uv+v^2=(b+b^4)^2-2(b+b^4)(b^2+b^3)+(b^2+b^3)^2=b^2+2b^5+b^8-2b^3-2b^4-2b^6-2b^7_+b^4+2b^5+b^6
b^5=1 so we have b^2+2+b^3-2b^3-2b^4-2b-2b^2+b^4+b=(b^2+b^3-2b^3-2b^4-2b-2b^2+b^4+b)+4
=-(b^3+b^4+b +b^2)+4=5
« Last Edit: April 23, 2009, 09:31:13 pm by astarmathsandphysics »

Offline radam

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Re: Maths/Physics help
« Reply #82 on: April 23, 2009, 02:04:40 pm »
Ah thanks!

I forgot that b^5=1;

I was thinking about the question with that bit of insight; and i was wondering if my method below is correct:

(u-v) is the same as sqroot (u-v)^2 (since u-v>0)

(U-v)=u^2-2uv+v^2= b^8+2b^5+b^2+2+b^4+2b^5+b^6

since uv=-1, and b^5=1

This gives b^4+b^3+b^2+b-6= 5

Hence  (u-v)^2= 5

u-v= sqrt(5)

The answer seems correct, but I'm wary of squaring as it normally adds complications to the matter... is there an easier and less time consuming way to do it?

Again thanks a lot for your help! With my math exam 2 weeks away, its a life-saver!

Offline Clerk

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Re: Maths/Physics help
« Reply #83 on: April 28, 2009, 11:00:43 pm »
Hi. I'm a standard level physics student. Does anyone know if I have to know how to "Solve problems using the equation of state of an ideal gas". There are some past papers exercises, but I think that this part of the syllabus is now only for high level. Please help me!

Offline astarmathsandphysics

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Re: Maths/Physics help
« Reply #84 on: April 28, 2009, 11:06:34 pm »
Ah thanks!

I forgot that b^5=1;

I was thinking about the question with that bit of insight; and i was wondering if my method below is correct:

(u-v) is the same as sqroot (u-v)^2 (since u-v>0)

(U-v)=u^2-2uv+v^2= b^8+2b^5+b^2+2+b^4+2b^5+b^6

since uv=-1, and b^5=1

This gives b^4+b^3+b^2+b-6= 5

Hence  (u-v)^2= 5

u-v= sqrt(5)

The answer seems correct, but I'm wary of squaring as it normally adds complications to the matter... is there an easier and less time consuming way to do it?

Again thanks a lot for your help! With my math exam 2 weeks away, its a life-saver!

I can't think of a simpler way to do it.

Offline astarmathsandphysics

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Re: Maths/Physics help
« Reply #85 on: April 28, 2009, 11:07:12 pm »
Post your questions and I will answer asap

Offline IGSTUDENT

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Re: Maths/Physics help
« Reply #86 on: June 08, 2009, 10:11:13 am »
Can u pls suggest a good book for IB Higher maths ?Aslo for Chemisty HL?

Offline omega007

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Re: Maths/Physics help
« Reply #87 on: June 08, 2009, 11:43:55 am »
This is going to help you with the books.

http://en.wikibooks.org/wiki/IB_Textbook_Reviews

Offline IGSTUDENT

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Re: Maths/Physics help
« Reply #88 on: June 08, 2009, 12:58:37 pm »
Thanks a lot.Will have a look.
All the same some of you who are already doing it..any suggestions?

Offline IGSTUDENT

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Re: Maths/Physics help
« Reply #89 on: June 08, 2009, 12:59:18 pm »
Thanks a lot.Will have a look.
All the same some of you who are already doing it..any suggestions?