code:
a,t = var('a,t')
x = function('x', t)
y = function('y', t)
dx2 = diff(x,t,2) == -(1-a)*((x-a)/(sqrt((x-a)^2 +
y^2))^3)-a*((x+1-a)/(sqrt((x+1-a)^2 + y^2))^3)+x+2*diff(y,t,1)
dy2 = diff(y,t,2) == -(1-a)*(y/(sqrt((x-a)^2 +
y^2))^3)-a*(y/(sqrt((x+1-a)^2 + y^2))^3)+y-2*diff(x,t,1) desolve(dx2, x,
ics=[0,1])
error:
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
/home/eric/<ipython console> in <module>()
/home/eric/programs/sage-5.5/local/lib/python2.7/site-packages/sage/calculus/desolvers.pyc
in desolve(de, dvar, ics, ivar, show_method, contrib_ode)
418 ivars = [t for t in ivars if t is not dvar]
419 if len(ivars) != 1:
--> 420 raise ValueError, "Unable to determine independent variable, please
specify."
421 ivar = ivars[0]
422 def sanitize_var(exprs):
ValueError: Unable to determine independent variable, please specify.
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