Any suggestions to obtain $x$ in terms of $n$ in this equation. Again Mathematica gives: "This system cannot be solved with the methods available to Solve."
$\coth (\pi x) \coth (n x)-\frac{x^4-2 x^2+5}{4 \left(x^2-1\right)}=0$
Coth[n x] Coth[\[Pi] x] - (5 - 2 x^2 + x^4)/(4 (-1 + x^2)) == 0
Any comment to solve this equation is welcomed.
Answer
It should be noted that the type of numeric search, based on ContourPlot
, that others mention in the comments, has been automated by Wagon, in his book, Mathematica in Action. J.M. gives a version of Wagon's function in this answer.
Using his function, we get the following:
With[{n = 1},
FindAllCrossings[Coth[n x] Coth[π x] - (5 - 2 x^2 + x^4)/(4 (-1 + x^2)), {x, -5, 5}, WorkingPrecision -> 20]
]
{-1.9201894111730777583, -1.5082193798592498308}
Let's check to make sure that the solution are ok:
With[{n = 1},
Coth[n x] Coth[π x] - (5 - 2 x^2 + x^4)/(4 (-1 + x^2)) /.
x -> -1.92018941117307775830055191944881406955`20.
]
0.*10^-20
With[{n = 1},
Coth[n x] Coth[\[Pi] x] - (5 - 2 x^2 + x^4)/(4 (-1 + x^2)) /.
x -> -1.50821937985924983076925593990549242151`20.
]
0.*10^-19
Yup, it seems to be working.
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