Translate the following inference to logic notation: There is at least one x for which x_10 is sad or x_10 is not a musician. For all x, if x_10 were a musician, then x_10 is sad. For all x, if x_10 were sad, then x_10 is a musician. Therefore there is at least one x for which x_10 is sad if and only if x_10 is a musician.
exists x: P(x) or ~Q(x). forall x: Q(x) -> P(x). forall x: P(x) -> Q(x). Therefore exists x: P(x) <-> Q(x).