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user21820
user21820
01:49
@adeshmishra Didn't I say "following exercises" and then pasted 5 exercises?
Once you finish any one of them, post your attempt here, and I will check it.
Once you can finish all of them correctly, you will be ready to go on.
 
4 hours later…
adesh mishra
adesh mishra
06:17
@user21820 Ma’am I’m really sorry but I’m not able to understand what we have to do in those? Do I need to tell true or false? Or do I have to write it symbolically?
 
11 hours later…
user21820
user21820
16:52
@adeshmishra Don't call me "ma'am" or "sir" or anything. Use my username.
yesterday, by user21820
As I suggested earlier, look at the Examples linked from my profile under "Natural deduction", and go through the Rules up to "Boolean operations". If they seem to make sense for you, try the following exercises and post your attempts here (paste, then click "fixed font", then click "send"), and I will check them.
The Rules tell you what lines you can write, given what lines you have already written. A proof in this system must follow the rules and end with a line that is exactly the desired statement to be proven.
For example, here is a proof of "A∨¬A": 
If ¬(A∨¬A):	// ⇒sub
	¬(A∨¬A).	// ⇒sub
	If A:	// ⇒sub
		A.	// ⇒sub
		A∨¬A.	// ∨intro
		¬(A∨¬A).	// restate
		⊥.	// ¬elim
	¬A.	// ¬intro
	A∨¬A.	// ∨intro
	⊥.	// ¬elim
¬¬(A∨¬A).	// ¬intro
A∨¬A.	// ¬¬elim
I have labelled every single line with the rule that permitted it. But as stated in the Rules, omit repeated lines, so the proof should be written: 
If ¬(A∨¬A):	// ⇒sub
	If A:	// ⇒sub
		A∨¬A.	// ∨intro
		⊥.	// ¬elim
	¬A.	// ¬intro
	A∨¬A.	// ∨intro
	⊥.	// ¬elim
¬¬(A∨¬A).	// ¬intro
A∨¬A.	// ¬¬elim
 
2 hours later…
user21820
user21820
18:40
In case you don't know where "my profile" is, it's here.
 
3 hours later…
Roddy MacPhee
Roddy MacPhee
21:11
What are the logical equivalents using AND, OR, NEG or the other 13 Boolean logic gates ?
for *
I know A XOR B is (A AND NEG B) OR (NEG A AND B )

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