Results 1 to 3 of 3

Math Help - Vectors

  1. #1
    Newbie
    Joined
    Jun 2010
    Posts
    13

    Vectors

    find a vector of length 3 which has A.)the smae direction as 5i-2j
    B.)the opposite direction to 4i+5j
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor

    Joined
    Aug 2006
    Posts
    18,648
    Thanks
    1596
    Awards
    1
    Quote Originally Posted by rabih2011 View Post
    find a vector of length 3 which has A.)the smae direction as 5i-2j
    B.)the opposite direction to 4i+5j
    If v is a vector and k is a real number the \dfrac{|k|}{||v||}v is a vector in the direction of v with length |k|
    Follow Math Help Forum on Facebook and Google+

  3. #3
    MHF Contributor ebaines's Avatar
    Joined
    Jun 2008
    From
    Illinois
    Posts
    1,089
    Thanks
    314
    To be "in the same direction" means that the vector you're looking for has the same ratio of components i and j as the original vector. You're starting with the vector  5 \vec i - 2 \vec j, whose magnitude is \sqrt {29}. So to have a vector of magintude 3 in the same direction simply multiply  5 \vec i - 2 \vec j through by  3/\sqrt {29} .

    To be in the opposite direction of a given vector, simply reverse the signs or the  \vec i and  \vec j components. So the opposite of vector  4 \vec i + 5 \vec j is:  -4 \vec i - 5 \vec j . Then apply the same length correction as above.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 3
    Last Post: November 15th 2011, 05:10 PM
  2. Replies: 3
    Last Post: June 30th 2011, 08:05 PM
  3. Replies: 2
    Last Post: June 18th 2011, 10:31 AM
  4. [SOLVED] Vectors: Finding coefficients to scalars with given vectors.
    Posted in the Pre-Calculus Forum
    Replies: 2
    Last Post: January 23rd 2011, 12:47 AM
  5. Replies: 4
    Last Post: May 10th 2009, 06:03 PM

Search Tags


/mathhelpforum @mathhelpforum