–
can be written as a Hamiltonian system
for suitable (non-autonomous) Hamiltonian functions
.
The Hamiltonian for
is
and so
Then
satisfies
and
satisfies
The function
defined by
(32.6.9) satisfies
The Hamiltonian for
is
and so
Then
satisfies
with
The function
defined by (32.6.16) satisfies
Conversely, if
is a solution of (32.6.21), then