Hey,
I can't do a question and need help ugently, i have been asked to write;
"The Set A has at most 2 elements"
as a Logical Formulae. But have no idea how to go about it.
Thanks
D
Since you ask for a formula involving quantification, this is how I'd write it and how you would probably see it written
in most any textbook on axiomatic set theory. As you can see, there's no need for explicit mention of the empty set.
The key here is to recognize that it's a hypothetical statement.
(Note: 'e' denotes set membership; the other symbols should be obvious).
(x)(y)(z) [[(xeA ^ yeA) ^ ~(x = y)] -> [zeA -> [(z = x) V (z = y)]]]