Results 1 to 2 of 2

Thread: Vector product

  1. #1
    Senior Member
    Oct 2009

    Vector product

    I think I have done this question but is there a better way? Prove that if the numbers p, q, r and s satisfy ps=qr, then (pa+qb) x (ra+sb) = 0. a and b are vectors.
    Attached Thumbnails Attached Thumbnails Vector product-scan-1.jpg  
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor

    Apr 2005

    Re: Vector product

    It looks good to me though a little more complicated than necessary.

    $\displaystyle (pa+ qb)\times(ra+ sb)= pa\times ra+ pa\times sb+ qb\times ra+ qb\times sb$
    Of course, you can take out the numbers: pr(a\times a)+ ps(a\times b)+ qr(b\times a)+ qs(b\times b)[tex]
    $\displaystyle a\times a= b\times b= 0$ so that reduces to $\displaystyle ps(a\times b)+ ar(b\times a)= ps(a\times b)- qr(a\times b)= (ps- qr)(a\times b)$.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. scalar product and vector product combined
    Posted in the Geometry Forum
    Replies: 12
    Last Post: Mar 30th 2012, 01:17 PM
  2. Replies: 5
    Last Post: Sep 7th 2011, 05:31 PM
  3. Replies: 6
    Last Post: Sep 7th 2010, 09:03 PM
  4. Vector product
    Posted in the Differential Geometry Forum
    Replies: 2
    Last Post: Oct 17th 2009, 02:04 PM
  5. dot product of vector
    Posted in the Pre-Calculus Forum
    Replies: 3
    Last Post: May 19th 2008, 05:04 PM

Search Tags

/mathhelpforum @mathhelpforum