Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Taking only the positive sqrt in Mathematica

  1. May 27, 2010 #1
    As my title says, I need to take only the positive square root of some evaluation. For my calculation, the negative square root is extraneous.

    What I do is a normalization of a wave function:

    Code (Text):
    J = Integrate[Psi[x]^2, {x, 0, a}]
    sol = Solve[J == 1, A]
    A /. sol
     
    My only problem is those above expression will give me A = {-1/sqrt(2), 1/sqrt(2)}.

    How can I force Mathematica to only give me positive square root?
     
  2. jcsd
  3. May 27, 2010 #2
    Code (Text):
    DeleteCases[A,x_/;x<0]
    This will ofc only work with expressions mathematica can evaluate numerically or knows to be positive or negative.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook