1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Points relative to vectors. And Eq of line. Vectors

  1. May 8, 2013 #1
    1. The problem statement, all variables and given/known data
    Find the coordinates of α, β, and γ rel. to u, p, q (unit vectors) of x = 1/9( 2i + 62j - 11k )(
    (Note there orthogonal to each other)

    Question 2 : The position vectors of two points A, B has position vectors a = < 2, 1, 7> and
    b = <1, 4,-1>
    Find the parametric vector eq of the line AB using lambda as parameter.
    2. Relevant equations

    For the first question I just did the dot product of x with each unit vector.
    I ended up with σ = 2 , β = 3 , γ = 6
    What do you think?


    For the next question please don't give me an answer give me a question to direct my though if it is incorrect. Thanks.


    So I said x = a + λb
    Where b is a unit vector. Is this proper? I didn't want to expand it and write the vectors it will look a mess.
    I have the unit vector b = < 1/ (3sqrt 3), 4/ (3 sqrt 3), -1/ (3sqrt 3)>
    I think this is proper.
     
  2. jcsd
  3. May 8, 2013 #2

    Mark44

    Staff: Mentor

    What are u, p, and q? All you said was that they are unit vectors that are orthogonal to each other.
    Didn't you post this as a separate question in your other thread?
     
  4. May 9, 2013 #3
    Mod note: Edited to properly show what was quoted.
    What do you mean what are they? I don't understand.
    Yeah I posted this first then I thought not to clump so just ignore the second question. Thanks.


    Sorry they are

    q = < 4/9 , 7/9 , -4/9 >
    u = < 1/9, 4/9 , 8/9 >
    p = < -8/9, 4/9 , -1/ 9>
     
    Last edited by a moderator: May 9, 2013
  5. May 9, 2013 #4

    Mark44

    Staff: Mentor

    The problem is to write x = <2/9, 62/9, -11/9> as a linear combination of u, p, and q.

    In other words, you want to find constants a, b, and c (didn't see the point in using Greek letters) so that
    x = au + bp + cq
     
  6. May 9, 2013 #5
    Yeah and I got σ = 2 , β = 3 , γ = 6, so x = 2u + 3p + 6q
    assuming that I kept that in the right order. and your a = alpha , b = beta, c = gamma.
    I just had greek because the problem used it.
     
  7. May 9, 2013 #6

    Mark44

    Staff: Mentor

    This letter -- σ -- is sigma (lower case). This one is alpha - α.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted