Status: Accepted
Owner: ----
Labels: Type-Defect Priority-High Solvers
New issue 1398 by ondrej.certik: solve(1/(5+x)**(S(1)/5)-9, x) fails
http://code.google.com/p/sympy/issues/detail?id=1398
In [9]: solve(1/(5+x)**(S(1)/5)-9, x)
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
/home/ondrej/repos/sympy/<ipython console> in <module>()
/home/ondrej/repos/sympy/sympy/solvers/solvers.pyc in solve(f, *symbols,
**flags)
207 f_ = f.subs(symbol, t**m)
208 if guess_solve_strategy(f_, t) != GS_POLY:
--> 209 raise TypeError("Could not convert to a
polynomial equation: %s" % f_)
210 cv_sols = solve(f_, t)
211 result = list()
TypeError: Could not convert to a polynomial equation: -9 + (5 +
_t**5)**(-1/5)
This was found out by doing:
In [1]: y = Function("y")
In [2]: soln = dsolve(Derivative(y(x),x)+sin(x)*y(x)**6,y(x))
In [3]: soln
Out[3]:
1
─────────────────
5 ⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽⎽
╲╱ C₁ - 5⋅cos(x)
In [4]: ypi = soln.subs(x, pi)
In [5]: ypi
Out[5]:
1
──────────
5 ⎽⎽⎽⎽⎽⎽⎽⎽
╲╱ 5 + C₁
In [6]: C1=Symbol("C1")
In [7]: solve(ypi-9, C1)
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
/home/ondrej/repos/sympy/<ipython console> in <module>()
/home/ondrej/repos/sympy/sympy/solvers/solvers.pyc in solve(f, *symbols,
**flags)
207 f_ = f.subs(symbol, t**m)
208 if guess_solve_strategy(f_, t) != GS_POLY:
--> 209 raise TypeError("Could not convert to a
polynomial equation: %s" % f_)
210 cv_sols = solve(f_, t)
211 result = list()
TypeError: Could not convert to a polynomial equation: -9 + (5 +
_t**5)**(-1/5)
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