Final answer:
The logical expression of the given statement can be notated as \(\\eg P \land \\eg Q\) and \(\\eg(\\eg R)\), where P, Q, and R represent Holmes playing the violin, asking Watson for the needle, and both being baffled by Moriarty, respectively.
Step-by-step explanation:
The statement 'Sherlock Holmes will neither play his violin nor ask Watson for the needle; nevertheless, neither he nor Watson will fail to be baffled by Moriarty' can be translated into logical symbols and expressions as follows:
Let P represent 'Holmes plays his violin', Q represents 'Holmes asks Watson for the needle', and R represents 'Holmes and Watson are baffled by Moriarty'.
The statement can then be written as:
\(\\eg P \land \\eg Q\) and \(\\eg(\\eg R)\)
This expression states that both P and Q are not true, and R is also true, which matches the original English statement. Notationally, the neither-nor construction is represented by negations combined with a conjunction, and the negation of a negation represents the word 'fail to'.