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: Finding a unit vector orthogonal to

  1. Sep 27, 2009 #1
    1. The problem statement, all variables and given/known data

    Find a unit vector that is orthogonal to both i + j and i + k.

    I know I can solve this using the cross product of the two. But This chapter is about
    dot product and not cross product.

    I am not sure how I could go about solving this problem using the properties of a dot product.

    This is just a review, in test I would use the cross product.
  2. jcsd
  3. Sep 27, 2009 #2
    Thinking about this, I think I could use this formula :

    A*B = |A||B| cos(theta);


    B / |B| = |A|cos(theta) / A

    Where A is the displacement vector from the given vector, and theta should be 90 deg.

    Thus I would find a unit vector, B, perpendicular to the displacement vector of the
    given vectors, which is parallel to Each of the 2 given vector.

    Is this assumption correct?
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook