Headaches are one effect that can come from inhalation of isopropyl alcohol. Isopropyl alcohol, or rubbing alcohol, is often used in the home or in medical facilities to treat various conditions or to sterilize instruments and skin. However, if isopropyl alcohol is inhaled there can be serious side effects.
1a) Definition of contradiction: A contradiction exists any time a proposition P is asserted to be true in conjunction with its negation, not-P. 1b) Definition of conjunction: A conjunction is a connective that joins two propositions.
Construct a truth table for the formula . A tautology is a formula which is always true --- that is, it is true for every assignment of truth values to its simple components. You can think of a tautology as a rule of logic. The opposite of a tautology is a contradiction, a formula which is always false. In other words, a contradiction is false for every assignment of truth values to its simple components. Example.