exercise, left as an
Used to complete a proof in technical books when one doesn't mind a handwave, or to avoid one entirely. The complete phrase is: "The proof [or "the rest"] is left as an exercise for the reader." This comment *has* occasionally been attached to unsolved research problems by authors possessed of either an evil sense of humour or a vast faith in the capabilities of their audiences.
[The Jargon File]
(1995-02-20)