Prove:
(1) R isTotalOnA ⇔ (∀x : A • ∃ y : Y • (x , y) ϵ R)
(2) R ; (S ∩ T) ⊆ (R ; S) ∩ (R ; T)
Not good enough.
Define all the terms.
What is "TotalonA"?
What does $\displaystyle \bullet $ mean?
These happen to be nonstandard symbols.
EDIT:
Why not learn to post in symbols? You can use LaTeX tags
[tex]\left( {\exists x} \right)[/tex] gives $\displaystyle \left( {\exists x} \right) $ is exists
[tex]\left( {\forall x} \right)[/tex] gives $\displaystyle \left( {\forall x} \right) $ is for all
[tex] \cup [/tex] gives $\displaystyle \cup $ is union
[tex] \cap [/tex] gives $\displaystyle \cap $ is intersection
[tex] \subseteq [/tex] gives $\displaystyle \subseteq $ is subset
[tex] \cup [/tex] gives $\displaystyle \cup $ is union
[tex] \in [/tex] gives $\displaystyle \in $ is element
[tex] \emptyset [/tex] gives $\displaystyle \emptyset $ is emptyset
[tex] \wedge [/tex] gives $\displaystyle \wedge $ is or
[tex] \vee [/tex] gives $\displaystyle \vee $ is and
[tex] \sqrt{x+1} [/tex] gives $\displaystyle \sqrt{x+1} $