# antisymmetric

• Mar 27th 2008, 04:16 PM
teeplkyl
antisymmetric
R = {(a,b) is an element of A cross B with (b,a) an element of R inverse}

Proof:
If R is antisymmetric, then R inverse is antisymmetric

-if you can not prove this I must show a counterexample thanks
• Mar 27th 2008, 06:07 PM
ThePerfectHacker
You need to show if R is antisymettric, meaning if a<=b and b<=a implies a=b. Then $R^{-1}$ has the same property. It should be clear how to do this by definition.
• Mar 27th 2008, 07:07 PM
Plato
If $(x,y) \in R^{ - 1} \wedge (y,x) \in R^{ - 1} \quad \Rightarrow \quad (y,x) \in R \wedge (x,y) \in R.$
But we know that $R$ is antisymmetric so $x=y$.