Hello Chris,
seems there are two pitfalls : one when not specifying ivar parameters for
desolve function call or using formal function f in the argument equation.
You can try code like thisShorter code is valid too when expanding
directly eq parameter (as done in SAGE help examples)..
#
What's wrong with :
sage: var(a,x)
(a, x)
sage: z=function(z,x)
sage: f(x)=2*x+2*z*diff(z,x)/sqrt(x^2+a^2+z^2)
sage: f
x |-- 2*z(x)*D[0](z)(x)/sqrt(a^2 + x^2 + z(x)^2) + 2*x
hmmm ? You can also write :
sage: foo(x)=2*x+2*z(x)*diff(z(x),x)/sqrt(x^2+a^2+z(x)^2)
sage: foo
x |--
