Incidentally, trying trigsimp with recursive=True, deep=True, or both True
didn't give the desired result.
On Tue, Apr 28, 2009 at 12:22 AM, Luke <hazelnu...@gmail.com> wrote:
> I'm writing some tests for some code that expresses a Vector expression in
> the coordinates of a different frame. I am using Sympy's trigsimp to
> simplify expressions, but the following Sympy expression isn't
> trigsimplifying:
> cos(q4)**2 + sin(q3)**2*sin(q4)**2 + cos(q3)**2*cos(q4)**2*tan(q4)**2
>
> It should simplify to 1, instead it trigsimplifies to:
> cos(q4)**2 + sin(q3)**2*sin(q4)**2 + cos(q3)**2*sin(q4)**2
>
> So, I tried trigsimplifying, then factoring, but I got the following error:
>
> In [10]: factor(trigsimp(cos(q4)**2 + sin(q3)**2*sin(q4)**2 +
> cos(q3)**2*cos(q4)**2*tan(q4)**2))
> ERROR: An unexpected error occurred while tokenizing
> input
> The following traceback may be corrupted or invalid
> The error message is: ('EOF in multi-line statement', (33, 0))
>
> ---------------------------------------------------------------------------
> PolynomialError Traceback (most recent call last)
>
> /home/luke/Documents/PythonDynamics/<ipython console> in <module>()
>
> /usr/lib/pymodules/python2.5/sympy/polys/factortools.pyc in factor(f,
> *symbols, **flags)
> 78 return f
> 79
> ---> 80 coeff, factors = poly_factors(f, *symbols, **flags)
> 81
> 82 result = 1 # XXX: don't include coeff in the leading factor
>
> /usr/lib/pymodules/python2.5/sympy/polys/factortools.pyc in poly_factors(f,
> *symbols, **flags)
> 18 """
> 19 if not isinstance(f, Poly):
> ---> 20 f = Poly(f, *symbols)
> 21 elif symbols:
> 22 raise SymbolsError("Redundant symbols were given")
>
> /usr/lib/pymodules/python2.5/sympy/polys/polynomial.pyc in __new__(cls,
> poly, *symbols, **flags)
> 400 terms = Poly._permute(poly, *symbols)
> 401 else:
> --> 402 terms = Poly._decompose(poly, *symbols)
> 403
> 404 if terms:
>
> /usr/lib/pymodules/python2.5/sympy/polys/polynomial.pyc in _decompose(poly,
> *symbols)
> 543 continue
> 544
> --> 545 raise PolynomialError("Can't decompose %s"
> % factor)
> 546 else:
> 547 coeff *= factor
>
> PolynomialError: Can't decompose cos(q4)**2
>
>
> I'm dealing with stuff that is going to make heavy use of trigsimp, so I'm
> willing to dig into it a bit.
>
> Should this be filed as a bug, or is there something obvious that I am
> missing.
>
> Thanks,
> ~Luke
>
>
>
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