354. Give an example of a function that, for $x$ equal to any of the numbers $a_{1}, a_{2}, a_{3} \ldots a_{n}$, would be equal to: 1) zero, 2) a given number $k$.
354. a) $\left(x-\alpha_{1}\right)\left(x-\alpha_{2}\right)^{2}\left(x-\alpha_{3}\right)^{3} \ldots\left(x-\alpha_{n}\right)^{n}$
b) $\sin \left(x-\alpha_{1}\right) \sin \left(x-\alpha_{2}\right) \ldots \sin \left(x-\alpha_{n}\right)+$ $+k \cos \left(x-\alpha_{1}\right) \cos \left(x-\alpha_{2}\right) \ldots \cos \left(x-\alpha_{n}\right)$.