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Re: What is the inverse function of -- y = 2 ^ (x / 18) + (x / 5)
Posted:
Dec 16, 2001 2:27 AM
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"David W. Cantrell" wrote:
> "Shamoon Siddiqui" <webmaster@visionsofdreams.com> wrote:
> > It won't be a simple algebraic answer.
>
> True, but not surprising since the original function is given in terms
> of a transcendental function. Maybe you had in mind that the inverse
> function cannot be written in closed form in terms of "familiar" functions.
> That is correct. However, if one is willing to use the Lambert W function
> (for which information is available on the web, e.g. at
> ),
> then the inverse function can be given in closed form. Using the principal
> branch of the Lambert W function and letting c = 5/18*ln(2), the inverse
> function is y = 5( x - W(c*e^(c*x))/c ).
Nonetheless, a simpler solution would be to ask OP if (s)he is seeking the
inverse function of 2^((x/18)+(x/5)). Just to make sure.
Jon Miller
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