# Error/warning when using NSolve for simple equation

I am using NSolve to solve an equation, as shown here:

T == (0.000250709 E^(0.0269867/(0.0000734429 + 1. T)))/(1.00025 -
1. E^(0.0539734/(0.0000734429 + 1. T)))

NSolve[T == (0.000250709 E^(0.0269867/(0.0000734429 +
1. T)))/(1.00025 -
1. E^(0.0539734/(0.0000734429 + 1. T))), {T}, Reals]


It gives me the warning Solve::ratnz: Solve was unable to solve the system with inexact coefficients. The answer was obtained by solving a corresponding exact system and numericizing the result. >>, but still displays the result. Is it wrong to use NSolve for for such a general task, or am I missing a parameter?

No errors if you work with exact arithmetic instead:

NSolve[Rationalize[
T == (0.000250709 E^(0.0269867/(0.0000734429 + 1. T)))/
(1.00025 - 1. E^(0.0539734/(0.0000734429 + 1. T))), 10^-10], {T}, Reals]

(*{{T -> -6.55871*10^-164}, {T -> 216.923}}*)

• It works, thanks.. but I'm not sure why. Does NSolve have an issue working with high precision? – BillyJean May 1 '13 at 13:35
• @niles, it's just that NSolve[] has some trouble if inexact numbers are present in the input. That's where Rationalize[] comes in. – J. M. will be back soon May 15 '13 at 11:49