Exercise:

FORALL x(I) [P(OI) x EQUIV EXISTS y(I) P y] EQUIV .FORALL x P x EQUIV EXISTS y P y

You may not use ADVICE, but all other rules and commands are allowed.

Only book theorems may be ASSERTed as lemmas without proof.

For a complete list of book theorems, type PROBLEMS.

No more help available. Sorry.

© 1988-99, Carnegie Mellon University.