Propositional Equivalences

Compound propositions that have the same truth values in all possible cases are called logically equivalent. You can find notes here

LOGIC

In order to understand math, you must understand principle definitions.  In order to understand and believe these statements, you must understand Logic.  The rules of logic give precise meaning to mathematical statements.  These rules are used in order to distinguish between valid and invalid mathematical arguments.  To understand logic is to understand the truth of logic.

You can download Logic document here.