The proving principle by contraposition is a valid logical argument. For two propositions $p$ and $q$, it consists of $$\begin{array}{rll} \neg q\Rightarrow \neg p&\text{premise}&\text{e.g. If the roads are not wet, then it is not raining.}\\ \hline p\Rightarrow q&\text{conclusion}&\text{e.g. If it is raining, then the roads are wet.}\\ \end{array} $$
Proofs: 1
Chapters: 1
Definitions: 2
Examples: 3
Explanations: 4
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Propositions: 22 23