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Evaluate limit relation between variables in Mathematica

  1. Aug 22, 2012 #1
    Hello.
    How do I evaluate, in Mathematica, limits like this:
    "X+Y" when X is much bigger than Y, i.e., when Y/X->0. The unswer should be X+Y->X.

    Regards.
     
  2. jcsd
  3. Aug 22, 2012 #2
    I've never seen Mathematica take limits with respect to an expression. All the examples I've seen take limits with respect to a variable.

    Perhaps you could see how to use this:

    In[1]:= x+y/.y->10.^-100x

    Out[1]= 1. x
     
  4. Aug 28, 2012 #3

    Hepth

    User Avatar
    Gold Member

    I always just use a scale variable and expand.

    let z = x/y:

    F[x_, y_] := x + y
    Normal[Series[F[x, z x], {z, 0, 0}]]
     
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