Remember, what you trying to teach me is a universal physical and
mathematical LAW of 1/r^2. I say it doesn't apply to dish antennae.

**** It does apply to dish antenna once you get far enough away. Far enough
away is

r >> d^2/w

Where d = aperture and w = wavelength.

There is nothing at all unusual about this; all non-point sources have
similar rules. The light from a flurescent light is not 4 times as strong 1
mm from the surface as it is 2 mm from the surface; the light flux is almost
exactly the same. A flourescent tube does not display an iverse square law
unless

Where l is the length of the tube.

R. Srinivasan wrote:

Konrad Viltersten wrote:

I exhibit no typo's. Let me re-phrase. The urinary member is present
with a 0.5 probability in the general population, for which the
addition of the remaining urinary structure comprises a probability of
1.

Konrad Viltersten wrote:

How can one show that the following is a tautology by means of
natural deduction?

(a) OR (NOT a)

I've tried to use the truity and different approaches with
eliminations and introductions but i can't make it work. If
it's possible, i'd prefer a hint before a spoiling straight
forward answer.

--
Vänligen
Konrad
---------------------------------------------------

Sleep - thing used by ineffective people
as a substitute for coffee

Ambition - a poor excuse for not having
enough sence to be lazy
---------------------------------------------------

Hello,
,
Does anybody knows how to prove
(Ax)(Fx & Gx) <--> ~(Ex) (Fx -> ~Gx)

using only primitive natural deduction rules?

from left to right
(Ax)(Fx & Gx) |- ~(Ex) (Fx -> ~Gx)

i get as far as
1 (1) (Ax)(Fx & Gx) Premisse
2 (2) (Ex)(Fx -> ~Gx) Assumption
3 (3) Fa -> ~Ga 2 ES /Ass
1 (4) Fa & Ga 1 US
1 (5) Fa 1 &E
1 (6) Ga 1 &E
1,3 (7) ~Ga 5,3 MP / ->E
1,3 (8) Ga & ~Ga 6,7 &I
1 (9) ~(Ex)(Fx -> ~Gx)1,2-8 RAA ??????

but I am not sure if RAA is used here according to the rules
maybe only ~(Fa -> ~Ga) is derivable here so i got stuck there