problem solving equation systems

asked 2017-03-02 09:33:42 -0500

var('V1', 'V2') solve([V1+V2==0.5,7.20 == 5.5 - log(V1/V2,10)], V1, V2)

SageMath do not solve this system but when with Ctrl+C the calculation end and show in terminal the solution.

If I use natural logarithm in the expression Sage solve this system without any problem.

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I can not reproduce your problem, on 7.6.beta5 i got:

sage: var('V1', 'V2') ; solve([V1+V2==0.5,7.20 == 5.5 - log(V1/V2,10)], V1, V2)
(V1, V2)
[[V1 == 1/2/(e^(1914029841632461/1125899906842624*log(10)) + 1), V2 == 1/2*e^(1914029841632461/1125899906842624*log(10))/(e^(1914029841632461/1125899906842624*log(10)) + 1)]]

Could you please give us some informations so that someone can try to reproduce your problem:

  • which version of Sage did you use ?
  • which OS ?
  • did you install Sage from the binaries, and which ones ?
  • did you compile Sage yourself ?
  • which notebook did you use (Sage notebook or jupyter notebook) ?
  • did you use the command line ?
  • ... ?
tmonteil gravatar imagetmonteil ( 2017-03-02 10:25:45 -0500 )edit

The ?solve gives me:

Algebraically solve an equation or system of equations (over the complex numbers) for given variables.

But we do not have an algebraic system. For a numerical solution one can substitute V2 from the first in the second, plot and/or use (in my case pari/gp) solve.

dan_fulea gravatar imagedan_fulea ( 2017-03-05 10:50:10 -0500 )edit