vectors how to do this?

• Bigcable22

  15 Nov 08, 18:21

  Six points A,B,C,D,E and F are given.    P,Q,R and S are the centroids of the triangles ABC,ABD,DEF, and CEF respectively. The centroid of triangle ABC has the position vector 1/3(a+b+c) and centroid of triangle ABD has the position vector 1/3(a+b+d) given that position vector of D is d.(Position vectors of E and F are not given)

  Show that P,Q,R,S are the vertices of a parallelogram.

• wee_ws

  17 Nov 08, 07:36

  Hi,

    Given two centroids, we can obtain the position vectors R and S in a similar fashion:

   

   

    Now, what is left to be shown are the following:

     and

    which are straightforward. Try it!

• wee_ws

  17 Nov 08, 08:03

  Sorry, I have placed the response on my website, since I'm unable to include an attachment to explain the Greek symbols :P

  It is available at: http://www.freewebs.com/weews/sgforumresponse.htm

  Cheers,
  Wen Shih

• eagle

  17 Nov 08, 08:30

  hey weews

  thanks for your help

  you can actually add in greek symbols as well from the CharMap function in windows

  Start->run->charmap

• wee_ws

  17 Nov 08, 12:05

  Hi,

    Thanks, but charmap may be limited when it comes to representing vectors with arrows on top. Can Latex be supported in this forum?

    Thanks again!

  Cheers,
  Wen Shih

• eagle

  17 Nov 08, 15:58

  Originally posted by wee_ws:

  Hi,

    Thanks, but charmap may be limited when it comes to representing vectors with arrows on top. Can Latex be supported in this forum?

    Thanks again!

  Cheers,
  Wen Shih

  tried before... can't