Qualification > Math
Math P1
nid404:
I have to brush up on maths now. Will do it when I come back
ny:
hello.i have this vector question for P1.
actually it was my mock exam question.
the question is:
the points A and B are such that the unit vector in the direction AB(from A to B) is 1/3i + pj +2/3k , where p is a negative constant.
i) find the value of p
then, the position vectors of A and B, relative to an origin O, are 9i +2j +qk and 12i -4j -5k respectively.
ii) find the value of q
thats all.thank you soo much.please reply asap..
Monica:
--- Quote from: thecandydoll on May 10, 2010, 03:38:58 pm ---I really dont know to how to get the values?!!?!
i understand solving 2d vectors
But when the image is given i just cant.
how should i proceed!
cie as p1,nov 2007 :)
please,explain
Thank you.
--- End quote ---
10)i) PR= 2i + 2j +2k
PQ= -2i+2j+4k
ii) QPR is PQ and PR. When they say scalar you have to do this a.b(a multiplied by b) so PQ.PR = 2(-2) + 2(2) + 2(4) = -4 + 4 +8 =8
Now to get an angle you should know this formula : Cos (theta) = a.b/ |a|x|b|
we got a.b, so now |a| and |b|
|PR| = square root of (2^2 + 2^2 +2^2) = square root of 12
|PQ|= square root of (-2^2 + 2^2 + 4^2) = square root of 24
cos QPR = 8 / square root of 12 x square root of 24
iii) to get the perimeter you will need to get the position vector of PR, PQ and QR, make them under square root each and then add. Now you already got for PR and PQ in part i) so only QR is missing which is 4i +0j - 2k.
square root each of them and add them to get the perimeter.
Nothing is there, all you need to do is look at the image and match lines. Just look carefully with full concentration.
@Nid, how do you write the square roots, brackets, theta, etc?
nid404:
Thanks Mony.
You use latex symbols...you see that symbol of pi...you type text within that...http://www.artofproblemsolving.com/Wiki/index.php/LaTeX:Commands
Monica:
--- Quote from: ny on May 11, 2010, 02:53:34 am ---hello.i have this vector question for P1.
actually it was my mock exam question.
the question is:
the points A and B are such that the unit vector in the direction AB(from A to B) is 1/3i + pj +2/3k , where p is a negative constant.
i) find the value of p
then, the position vectors of A and B, relative to an origin O, are 9i +2j +qk and 12i -4j -5k respectively.
ii) find the value of q
thats all.thank you soo much.please reply asap..
--- End quote ---
I solved all the vectors questions so can you just post the paper and I'll post my answer?
@Nid..ahh thank you! Seems confusing but I'll just bookmark this page to use. =]
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