- #1

- 78

- 1

[tex]

\frac{\urcorner P \equiv false}{P \equiv true}

[/tex]

here is what I did

using Leibniz

[tex]

\frac{X \equiv Y}{E[z:=X] \equiv E[z:=Y]}

[/tex]

[tex]

X=\urcorner P

[/tex]

[tex]

Y=false

[/tex]

[tex]

E:\urcorner z

[/tex]

[tex]

z=z

[/tex]

[tex]

\frac{\urcorner P \equiv false}{\urcorner\urcorner P \equiv \urcorner false}

[/tex]

since [tex]\urcorner\urcorner P \equiv P[/tex]

and [tex]\urcorner false \equiv true [/tex]

[tex]

\frac{\urcorner P \equiv false}{P \equiv true}

[/tex]

is this a proof?