Hi folks. Long-time lurker, first-time poster. Anyways, my question regards the legitimacy of a contradiction-contrapositive hybrid method of proving.(adsbygoogle = window.adsbygoogle || []).push({});

Let's say we need to prove P implies Q. Contradiction says: If P implies Q_not leads to a contradiction, then we are done. Contrapositive says: If Q_not implies P_not, then we are done.

So a Contradiction-Contrapositive hybrid consists of first applying contradition, and then applying contrapositive. For example: To prove P implies Q by contradiction, we need to show P implies Q_not leads to a contradiction. But if we can also show that P_not implies Q leads to a contradiction, then are we done?

Is this method of proving legit?

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# Contradiction-Contrapositive hybrid

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