I am reading the book Elements of Discrete Mathematics by C L Liu. On the first chapter about Sets and Propositions, under the heading TAUTOLOGIES the author states
It may be observed that the conjunction of a tautology is also a tautology. The negation of a tautology is also a tautology.
How is this true? OR It is not true and just a mistake that needs to be corrected?
It is wrong (it must be a typo...).
The negation of a tautology is a formula that is Always FALSE, i.e. a contradiction.
Note added June 27.
I've browsed the Second Ed. (1985) of Liu's textbook and I've not found the wrong statement.