kkleiner writes: "Following its resounding victory on Jeopardy!, IBM’s Watson has been working hard to learn as much about medicine as it can with a steady diet of medical textbooks and healthcare journals. In a recent demonstration to the Associated Press Watson demonstrated a promising ability to diagnose patients. The demonstration was a success, and it is the hope of IBM and many medical professionals that in the coming years Watson will lend doctors a helping hand as they perform their daily rounds."
We warn the reader in advance that the proof presented here depends on a
clever but highly unmotivated trick.
-- Howard Anton, "Elementary Linear Algebra"