I came across this question:
The binary relation $S=\phi$ (empty set) on set $A=\{1,2,3\}$ is
a) Neither reflexive nor symmetric
b) Symmetric and reflexive
c) Transitive and refelxive
d) Transitive and symmetric
Please tell me if my understanding is correct:
For example, let $A=\{1,2,3\}$ then $A\times A=\{(1,1),(1,2),(1,3),(2,1),(2,2),(2,3),(3,1),(3,2),(3,3)\}$
and we are asked to do something as $1S1,1S2$...etc?
This is as far as I can understand it
Hint Go back to the definitions:
$S$ is reflexive iff for every $x\in A$, we have $(x,x)\in S$. Since there are no pairs $(a,b)\in S$, what can you conclude?
$S$ is symmetric iff whenever $(x,y)\in S$ then $(y,x)\in S$. Since there are no pairs $(x,y)\in S$, what can you conclude?
$S$ is transitive iff ... . What can you conclude?