I want to solve
$-F''(a) + e(a)( F'(a) - F(a)$
My code is
a = var('a')
e(a)= 1 /(1 + e^(-(a)))
F = function('F', a)
de = -diff(F,a, 2) + e(a)*(diff(F,a,1) - F(a))
y = desolve(de, F); y
But I get an error (at the end of the post). If I remove e(a)
from the de
-term, I get a solution. What do I have to take into account when I add the second function?
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "_sage_input_33.py", line 10, in <module>
exec compile(u'open("___code___.py","w").write("# -*- coding: utf-8 -*-\\n" + _support_.preparse_worksheet_cell(base64.b64decode("YSA9IHZhcignYScpCmUoYSk9IDEgLygxICsgZV4oLShhKSkpICAKRiA9IGZ1bmN0aW9uKCdGJywgYSwgaykKZGUgPSAtZGlmZihGLGEsIDIpICsgZShhKSooZGlmZihGLGEsMSkgLSBGKGEpKQp5ID0gZGVzb2x2ZShkZSwgRik7IHk="),globals())+"\\n"); execfile(os.path.abspath("___code___.py"))
File "", line 1, in <module>
File "/private/var/folders/r_/9cc9_ldj7g35cqnfql52hqt80000gn/T/tmpgTQRvn/___code___.py", line 7, in <module>
exec compile(u'y = desolve(de, F); y
File "", line 1, in <module>
File "/Applications/Sage-6.6.app/Contents/Resources/sage/local/lib/python2.7/site-packages/sage/calculus/desolvers.py", line 443, in desolve
raise ValueError("Unable to determine independent variable, please specify.")
ValueError: Unable to determine independent variable, please specify.