The document discusses propositional and predicate calculus as frameworks for representing mathematical discourse through formulas constructed using logical connectives. It defines various logical operations such as conjunction, disjunction, and negation, along with examples illustrating their application. The concepts of validity and satisfiability of formulas are also introduced, emphasizing the relationship between valid and satisfiable formulas.
SYNTAX OF PROPOSITIONALCALCULUS
Strings are known as Formulas.
A formula is constructed with the aid of Logical Connectives such
as AND,OR, NOT denoted by the symbols ^,v,¬
4.
• The wordblueberry has
two consecutive r’s
OR
• The word peach has six
letters
A : the word blueberry
has two consecutive r’s
B :the word peach has
six letter
(A V B)
5.
A :Stands for the word
“ watermelon has nine
letters,”
B : Stands for the word
“ blueberry has two
consecutive r’s , “
C : Stands for the word
“peach has six letters “
(A ^(B v ¬C)
6.
“ EitherJim or John is
here , but not both “
Jim is here or John is here
AND
John is not here or Jim is
not here
((A V B) ^ (¬A V ¬B))
Jim is here or John is
here;
AND
It is not the case that Jim
is here AND John is here
((A V B) ^ ¬ (A ^ B))
7.
DEFINITION
The formulasof the propositinal calculus are the
strings generated by the following CFG
G = (V,∑,R,S)
V = ∑ U {S,N}
∑ = { A,I,S,V,^,¬(,)}
R = { N ->e
N ->NI
S ->AN$
S ->(S V S)
S ->(S ^ S)
S -> ¬S }
8.
If F andG are any two formula
o ( F ^ G ) :- Conjunction of F and G
o ( F v G ) :- Disjunction of F and G
o ¬ F :- Negation of F
o ( F -> G) :- If F then G
( F -> G) = ( ¬F V G )
(F <-> G) = ( (F->G) ^ (G -> F) )
9.
A B (AV B)
T T T
T F T
F T T
F F F
DISJUNCTIONCONJUNCTION
A B (A ˄ B)
T T T
T F F
F T F
F F F
10.
NOT
A ¬ A
TF
F T
CONDITIONAL
A ¬ A B
(A -> B)
=(¬A V B)
T F T T
T F F F
F T T T
F T F T
11.
VALIDITY & SATISFIABILITY
VALIDITY
F is valid , if every truth
assignment appropriate to
F verifies.
i.e , F is a Tautology
SATISFIABILITY &
UNSATISFIABILITY
SATISFIABLE :- If the truth
table for the formulas
contains atleast one T’s.
UNSATISFIABLE :- If the
truth table for the formulas
contains all False.
“ EVERY VALID FORMULA IS SATISFIABLE. BUT EVERY
SATISFIABLE FORMULA IS NOT VALID ”