Example 1: If it is a square it has four sides; it is a square; therefore it has four sides. Valid affirmation of the antecedent.
Example 2: If it is a square it has four sides; it has four sides; therefore it is a square. Invalid affirmation of the consequent; a non-square rectangle is a counterexample.
Example 3: It is a triangle or square; not a triangle; therefore a square. Not licensed by exclusion of conjunction alone; it might be a circle.
Example 4: The number is at least 5 or at most 5; not at most 5; therefore at least 5. Valid denial-to-affirmation in exclusion of emptiness.