  We prove that the AdS/CFT calculation of 1-point functions can be drastically
simplified by using variational arguments. We give a simple universal proof,
valid for any theory that can be derived from a Lagrangian, that the large
radius divergencies in 1-point functions can always be renormalized away (at
least in the semiclassical approximation). The renormalized 1-point functions
then follow by a simple variational problem involving only finite quantities.
Several examples, a massive scalar, gravity, and renormalization flows, are
discussed. Our results are general and can thus be used for dualities beyond
AdS/CFT.
