Expose exercise, left as an

exercise, left as an Technical Terms
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.