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When I want a numerical value with a precision of 50 digits...

N[1.15/(1 - E^-0.2)^2, 50]

Why is Mathematica not able to provide the desired solution?

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And I know that this is irrational and the given solution is not precise and besides Mathematica would provide more digits even if the solution is already precise in other cases.

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So what is the problem here and how can I get more digits?

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    $\begingroup$ Start with exact or at least higher precision input. You have machine numbers in the input at present so you will not be able to get a (reliable) high precision result. $\endgroup$
    – Daniel Lichtblau
    Commented Apr 30, 2014 at 16:09
  • $\begingroup$ Does this give you a hint: N[1.0, 50]? (1.0 is less precise than 1`50) Try: N[23/(20 (1 - 1/E^(1/5))^2), 50] $\endgroup$
    – rm -rf ♦
    Commented Apr 30, 2014 at 16:09
  • $\begingroup$ Alternatively, you could go to the Preferences dialog, Appearance tab, Numbers subtab, Formatting subtab, then change the "Number of digits displayed in output" to something larger than 6. This will give you more digits even with the machine precision input (although you will obviously run out of digits at some point due to the issues in the above comments). $\endgroup$
    – KAI
    Commented Apr 30, 2014 at 16:15
  • $\begingroup$ Okay, guys, this solved my problem. I avoided the machine numbers and calculated N[(1 + 15/100)/(1 - E^(-(2/10)))^2, 50]. $\endgroup$
    – Gab
    Commented Apr 30, 2014 at 16:17
  • $\begingroup$ Taking a look at the second example in the documentation for N would have answered your question. I'm voting to close. $\endgroup$
    – RunnyKine
    Commented Apr 30, 2014 at 16:35

1 Answer 1

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You have to avoid machine numbers. Calculate

(1 + 15/100)/(1 - E^(-(2/10)))^2

and you will get the solution with an ad libitum precision.

enter image description here

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