1. Not finding help here? Sign up for a free 30min 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!

U(dot)U != ||U||^2 help?

  1. Mar 31, 2009 #1
    1. The problem statement, all variables and given/known data

    well i am told basicly this
    |u|^2 = U dot U except when in using imaginary numbers
    i tried using the example below and a few others but it seems to always work for me :/
    but i need the process or to show this is not true

    2. Relevant equations

    ||u|| = U dot U in general not complex :/

    3. The attempt at a solution

    2i + 5
     
  2. jcsd
  3. Apr 1, 2009 #2

    CompuChip

    User Avatar
    Science Advisor
    Homework Helper

    What are u and U?
    Are they the same (U = u)?
    Is u a vector, of which |u| is the norm, or just a number of which |u| is the absolute value (for real numbers) or the modulus (for complex ones). Or is it a matrix, for which |u| is some matrix norm?

    If it is a number, it's rather easy to show.
    The modulus (length) of 2i + 5 is [itex]\sqrt{2^2 + 5^2}[/itex] which is not equal to (2i + 5)^2.

    In general, the correct expression is
    |u|^2 = u . u*
    where u* is the complex conjugate of u.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: U(dot)U != ||U||^2 help?
  1. Can u help me (Replies: 1)

  2. Can u help here (Replies: 8)

  3. Plz cn u help me (Replies: 2)

  4. Can u help me ? (Replies: 13)

  5. Integral of e^(-u^2) (Replies: 3)

Loading...