Comment #6 on issue 1304 by akshaysrinivasan: Integrate sqrt(x**2 + y**2)
fails
http://code.google.com/p/sympy/issues/detail?id=1304
Mateusz: You were right, I apologise for posting without looking closely.
I tried what you suggested, but ended up getting errors
sympy.polys.polynomial for
>>> integrate(sqrt(x**2-y**2),x)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/home/neptune/sympy-clean/sympy/utilities/decorator.py", line 55, in
threaded_decorator
return func(expr, *args, **kwargs)
File "/home/neptune/sympy-clean/sympy/integrals/integrals.py", line 381,
in integrate
return integral.doit()
File "/home/neptune/sympy-clean/sympy/integrals/integrals.py", line 133,
in doit
antideriv = self._eval_integral(function, x)
File "/home/neptune/sympy-clean/sympy/integrals/integrals.py", line 306,
in
_eval_integral
h = heurisch(g, x, hints=[])
File "sympy/integrals/risch.py", line 216, in heurisch
denom = reduce(lambda p, q: lcm(p, q, V), denoms)
File "sympy/integrals/risch.py", line 216, in <lambda>
denom = reduce(lambda p, q: lcm(p, q, V), denoms)
File "<string>", line 3, in lcm
File "/home/neptune/sympy-clean/sympy/polys/wrappers.py", line 23, in
_map_basic
result = f(*_conv_args(n, args), **kwargs)
File "/home/neptune/sympy-clean/sympy/polys/algorithms.py", line 366, in
poly_lcm
f = Poly(f, *symbols)
File "/home/neptune/sympy-clean/sympy/polys/polynomial.py", line 402, in
__new__
terms = Poly._decompose(poly, *symbols)
File "/home/neptune/sympy-clean/sympy/polys/polynomial.py", line 545, in
_decompose
raise PolynomialError("Can't decompose %s" % factor)
sympy.polys.polynomial.PolynomialError: Can't decompose (y**2 -
_x3**2)**(1/2)
-----------------
Here's the code.
diff --git a/sympy/integrals/risch.py b/sympy/integrals/risch.py
index 81e2b7a..7ef3204 100644
--- a/sympy/integrals/risch.py
+++ b/sympy/integrals/risch.py
@@ -186,12 +186,12 @@ def heurisch(f, x, **kwargs):
elif g.is_Pow:
if g.exp.is_Rational and g.exp.q == 2:
M = g.base.match(a*x**2 + b)
-
- if M is not None and M[b].is_positive:
+ if M is not None :
if M[a].is_positive:
terms.add(asinh(sqrt(M[a]/M[b])*x))
elif M[a].is_negative:
terms.add(asin(sqrt(-M[a]/M[b])*x))
+
else:
--------------------
Is this related to issue 1323 ?
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