Prefix 「The eorem Any proper initial segement of a well-defined proposition contains an excess of left parenthesis. Thus no proper initial segement of a well defined propositon can itself be a well defined propositions Prove it by induction from simple to complicated propositionsPrefix . Theorem . . Any proper initial segement of a well-defined proposition contains an excess of left parenthesiss. Thus no proper initial segement of a well defined propositon can itself be a well defined propositions. . Proof. . . Prove it by induction from simple to complicated propositions. Yi Li (Fudan University) Discrete Mathematics(II) March 26, 2013 7 / 20