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Re: Inverse of function

  • To: mathgroup at
  • Subject: [mg121413] Re: Inverse of function
  • From: Simon <simonjtyler at>
  • Date: Wed, 14 Sep 2011 05:14:51 -0400 (EDT)
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  • References: <j4neqn$54e$>
  • Reply-to: comp.soft-sys.math.mathematica at

Exactly what code did you use to get the inverse function?

In[1]:= f[x_] := x^2

In[2]:= InverseFunction[f][y]

During evaluation of In[9]:= InverseFunction::ifun: Inverse functions are being used. Values may be lost for multivalued inverses. >>

Out[2]= -Sqrt[y]

Of course, Solve, Reduce and WolframAlpha are a bit smarter than that

In[3]:= Solve[f[x] == y, x]
Out[3]= {{x -> -Sqrt[y]}, {x -> Sqrt[y]}}

In[4]:= WolframAlpha["inverse of f(x) = x^2", {{"Result", 1}, "Plaintext"}]
Out[4]= "f^(-1)(x) = \[PlusMinus]sqrt(x)"

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