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!

Homework Help: Dot product - Orthogonal

  1. Mar 9, 2010 #1
    By evaluating the dot product,

    find the values of the scalar s for which the two vectors
    b=X+sY and c=X-sY
    are orthogonal
    also explain your answers with a sketch:





    my working

    (X,sY).(X,-sY) has to equal 0 for them to be orthogonal

    x.x = 1 since they are unit vectors
    sY.-sY = -1 to make the whole thing 0

    s = 1
    1*y . -1*y = -1

    1-1 =0

    sketch would be two vectors perpendicular to one another?
     
  2. jcsd
  3. Mar 9, 2010 #2
    could someone please inform me If my work is correct?
    cheers
     
  4. Mar 9, 2010 #3

    Mark44

    Staff: Mentor

    (X + sY).(X - sY) = 0
    ==> X.X + sY.X - sX.Y -s2Y.Y = X.X - s2Y.Y = 0
    ==> 1 - s2 = 0

    You found one solution for s; there are two.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook