HERMIA. I frown upon him, yet he loves me still.
HELENA. O that your frowns would teach my smiles such skill!
For 30 years Haydn lived and worked at the Esterhazy palace, largely isolated from what was happening elsewhere. As he himself recalled, "My prince was content with all my works, I received approval, I could, as head of an orchestra, make experiments, observe what created an impression, and what weakened it, thus improving, adding to, cutting away, and running risk. I was set apart from the world, there was nobody in my vicinity to confuse and annoy me in my course, and so I had to become original."
Given an equation involving the operations of union, intersection and taking complements of sets we can obtain a new equation by interchanging unions and intersections and by replacing each set by its complement.