# And

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If and are propositions, then " and " is a proposition (written ); it is true if both is true and is true.

To prove " and ", you can separately prove and then prove .

If you have already proved (or assumed) and , you can conclude . You can also conclude .

To disprove " and ", you must either disprove or disprove . Put another way, the logical negation of " and " is "not or not ".