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October 14, 2025, 05:45:20 am
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Author Topic: dejan91's questions  (Read 16991 times)  Share 

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dejan91

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Re: dejan91's questions
« Reply #15 on: March 29, 2009, 12:24:02 pm »
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Help please? :)

Find the cartesian equation of the path of an object whose position is given by the vector equation .
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TrueTears

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Re: dejan91's questions
« Reply #16 on: March 29, 2009, 12:29:13 pm »
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  ...[1]

  ...[2]

from [1], t = 2x sub into 2





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kurrymuncher

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Re: dejan91's questions
« Reply #17 on: March 29, 2009, 01:27:09 pm »
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remember to restrict the domain if your asked to graph it
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dejan91

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Re: dejan91's questions
« Reply #18 on: March 29, 2009, 02:02:26 pm »
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ohk yup thanks will remember
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dejan91

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Re: dejan91's questions
« Reply #19 on: March 29, 2009, 03:50:02 pm »
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Quote from: /0 on February 08, 2009, 10:23:23 pm
Quote from: dejan91 on February 08, 2009, 09:41:36 pm
Thanks Mao fo help anyway (Y)

Also, this isn't on vector proofs, but cbf starting new thread. Had this question that I just left ages ago till now..

If a = 2i - 3j + k and b = -2i + 3j + k,
find a unit vector perpendicular to both a and b.
Let the vector perpendicular to both and be

Then, by the dot product:





Adding the two equations, we find that and so .

So a possible vector could be

And the unit vector would be

Forgot about this one lol...

Answer to it is actually

How do you get this?
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dcc

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Re: dejan91's questions
« Reply #20 on: March 29, 2009, 04:26:30 pm »
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If a = 2i - 3j + k and b = -2i + 3j + k,
find a unit vector perpendicular to both a and b.



Which is of course, a scalar multiple of the answer you arrived at doing much the same thing, hence you are correct, and the book is talking crap, as the vector they have given is not perpendicular to a or b.

Then of course you have the negative of this vector, and the unit vector of these vectors.
« Last Edit: March 29, 2009, 04:30:59 pm by dcc »
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dejan91

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Re: dejan91's questions
« Reply #21 on: March 29, 2009, 09:45:51 pm »
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Hmmmm, not sure what that was ^^ matrices? But ok, so the book is wrong?
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dekoyl

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Re: dejan91's questions
« Reply #22 on: March 29, 2009, 09:48:37 pm »
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Quote from: dejan91 on March 29, 2009, 09:45:51 pm
Hmmmm, not sure what that was ^^ matrices? But ok, so the book is wrong?
That was using the cross product as the cross product of two vectors is perpendicular to the two vectors. However it's not in the specialist course so unfortunately you can't use it in the exam. :P
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dejan91

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Re: dejan91's questions
« Reply #23 on: March 30, 2009, 08:17:33 pm »
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Quote from: dekoyl on March 29, 2009, 09:48:37 pm
Quote from: dejan91 on March 29, 2009, 09:45:51 pm
Hmmmm, not sure what that was ^^ matrices? But ok, so the book is wrong?
That was using the cross product as the cross product of two vectors is perpendicular to the two vectors. However it's not in the specialist course so unfortunately you can't use it in the exam. :P

Ahhh no wonder I didn't quite understand it :P

Ok, this one is on one of TT's vector worksheets.



I got:
for i.

  for ii.

Is this right?

I'm stuck on b. Not sure how to aproach this exactly.
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Over9000

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Re: dejan91's questions
« Reply #24 on: March 30, 2009, 08:27:52 pm »
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Quote from: dejan91 on March 30, 2009, 08:17:33 pm
Quote from: dekoyl on March 29, 2009, 09:48:37 pm
Quote from: dejan91 on March 29, 2009, 09:45:51 pm
Hmmmm, not sure what that was ^^ matrices? But ok, so the book is wrong?
That was using the cross product as the cross product of two vectors is perpendicular to the two vectors. However it's not in the specialist course so unfortunately you can't use it in the exam. :P

Ahhh no wonder I didn't quite understand it :P

Ok, this one is on one of TT's vector worksheets.

(Image removed from quote.)

I got:
for i.

  for ii.

Is this right?

I'm stuck on b. Not sure how to aproach this exactly.
Yes, youre answers to 9.a) are all good, I got same answers
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Over9000

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Re: dejan91's questions
« Reply #25 on: March 30, 2009, 08:34:15 pm »
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For b



     
|AB|=|AC|
from previous question

square both side




i just made x = lamda, so sub that back in
« Last Edit: March 30, 2009, 08:36:35 pm by Over9000 »
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dejan91

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Re: dejan91's questions
« Reply #26 on: March 30, 2009, 08:45:11 pm »
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Ok cool as. My method was right all along it seems I just used AB = 10i+ 2j  lol. Thanks dude (Y)
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Over9000

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Re: dejan91's questions
« Reply #27 on: March 30, 2009, 09:01:33 pm »
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No probs  :)
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dejan91

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Re: dejan91's questions
« Reply #28 on: March 31, 2009, 07:01:51 pm »
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Anyone done this question? It's on truetears' question sheet 3. If you have, are you able to post up answers just so i can check if mine are right?

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dejan91

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Re: dejan91's questions
« Reply #29 on: April 10, 2009, 04:39:13 pm »
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Bit stuck on this:
Find the intersection of the two relations and . Thanks.
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