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Suppose a statement form $\varphi$ always has value T or U. Show $\varphi$ is a classical tautology.

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    This question is quite badly formulated. What is T? What is U? Do you mean first-order or just propositional?2011-02-10
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    See http://en.wikipedia.org/wiki/Three-valued_logic2011-02-10
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    Did you write out the truth table?2013-06-19

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