Revision history [back]
 | 1 | initial version |
A bug in sympy, indeed.
Another workaround, using Sage's default solver (i. e. maxima's) and filtering afterwards:
sage: [s for s in solve([x^3-y^2==21/2, 3*x*y+y==23/5],[x,y], solution_dict=True) if s[x].is_real() and s[y].is_real()]
[{x: 2.21465033180194, y: 0.6017830609212481}]
Note: unless you have compelling reasons (e. g. speed) to use numerical approximations, taking advantage of Sage's ability to use exact representations of quantities defined in exact terms is usually a good idea...
| | 2 | No.2 Revision |
A bug in sympy, indeed.indeed. EDIT : No, it's a (non-) feature of Sage. From the docstring :
There are a few optional keywords if you are trying to solve a single equation. They may only be used in that context.
And below (i. e. in the "single equation" context :
"algorithm" - string (default: 'maxima'); to use SymPy's solvers set this to 'sympy'. Note that SymPy is always used for diophantine equations.
One may try to use directly the sympy solvers ; the point is to sympify the arguments (correctly...). And to convert the result back to Sage...
Another workaround, using Sage's default solver (i. e. maxima's) and filtering afterwards:afterwards :
sage: [s for s in solve([x^3-y^2==21/2, 3*x*y+y==23/5],[x,y], solution_dict=True) if s[x].is_real() and s[y].is_real()]
[{x: 2.21465033180194, y: 0.6017830609212481}]
Note: unless you have compelling reasons (e. g. speed) to use numerical approximations, taking advantage of Sage's ability to use exact representations of quantities defined in exact terms is usually a good idea...
