Exercise, Left As An: [from Technical Books] Used To Complete A Proof When One Doesn't Mind A {handwave}, Or To Avoid One Entirely.

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:exercise, left as an: [from technical books] Used to complete a
proof 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 humor or a vast faith in the
capabilities of their audiences.
-- The AI Hackers Dictionary

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