Results 1 to 6 of 6

Math Help - DOT Product

  1. #1
    Member
    Joined
    Jun 2006
    Posts
    165

    Question DOT Product

    The dot product [3 1 4]dot 2
    -1
    5 is.

    My answer is 25, but I'm not sure. Thanks for any help given.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Grand Panjandrum
    Joined
    Nov 2005
    From
    someplace
    Posts
    14,972
    Thanks
    4
    Quote Originally Posted by kwtolley
    The dot product [3 1 4]dot 2
    -1
    5 is.

    My answer is 25, but I'm not sure. Thanks for any help given.
    The dot product of two vectors [x_1,\ x_2,\ x_3] and [x_1,\ x_2,\ x_3] is:

    <br />
\bold{x}\cdot \bold{y}=\sum_{i=1}^3 x_i y_i = x_1y_1+x_2y_2+x_3y_3<br />
.

    In this case we have \bold{x}=[3,1,4] and \bold{y}=[2,-1,5], so:

    <br />
\bold{x}\cdot \bold{y}= 3\times 2+1\times (-5)+4\times 5=21<br />
.

    RonL
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Member
    Joined
    Jun 2006
    Posts
    165

    thank you

    I really needed help on that one. I was way off on seting it up. thanks again for checking
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Forum Admin topsquark's Avatar
    Joined
    Jan 2006
    From
    Wellsville, NY
    Posts
    9,920
    Thanks
    332
    Awards
    1
    Quote Originally Posted by CaptainBlack
    In this case we have \bold{x}=[3,1,4] and \bold{y}=[2,-1,5], so:

    <br />
\bold{x}\cdot \bold{y}= 3\times 2+1\times (-5)+4\times 5=21<br />
.

    RonL
    Hold on! There was a typo:

    The last line should read:
     \bold{x}\cdot \bold{y}= 3\times 2+1\times (-1)+4\times 5=25<br />
 .

    So you were correct, ktwolley.

    -Dan
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Grand Panjandrum
    Joined
    Nov 2005
    From
    someplace
    Posts
    14,972
    Thanks
    4
    Quote Originally Posted by topsquark
    Hold on! There was a typo:

    The last line should read:
     \bold{x}\cdot \bold{y}= 3\times 2+1\times (-1)+4\times 5=25<br />
 .

    So you were correct, ktwolley.

    -Dan
    Opps, there you go, you should always check what a helper writes.
    Hopefully they provide enough information that they have in fact done
    what they say they are doing

    RonL
    Follow Math Help Forum on Facebook and Google+

  6. #6
    Member
    Joined
    Jun 2006
    Posts
    165

    Smile Its alllllll good

    Thanks both of you. I check and recheck myself and other, but sometimes the problems are hard. Thanks again you guys here are a big help.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 3
    Last Post: October 18th 2011, 04:40 AM
  2. Replies: 6
    Last Post: September 7th 2010, 09:03 PM
  3. multivariable differential for inner product(scalar product)?
    Posted in the Differential Geometry Forum
    Replies: 2
    Last Post: October 23rd 2009, 05:40 PM
  4. Replies: 4
    Last Post: September 2nd 2009, 04:07 AM
  5. Replies: 1
    Last Post: May 14th 2008, 11:31 AM

Search Tags


/mathhelpforum @mathhelpforum