1. Statements & Truth Tables True or False This statement is true or false.? A T/F statement is a declarative sentence. It has a value of true or false, but not both at the same time. Thus the following two statements are equivalent: This statement is false. This statement is true and this statement is false. The latter is a simple contradiction of the form "A and not A", and hence is false.

2. TF Statements The sentence “Today is Thursday” is a TF statement since we can decide whether the sentence is true or false. The sentence “Lincoln was the first President of the United States” is a TF statement since we can decide whether the sentence is true or false. “Is it a bear?” is not a TF statement since it is a question, not a simple declarative sentence. “Sit down” is not a TF statement. It is a command, not a simple declarative sentence.

3. TF Statements/Negations To negate a TF statement is to change its truth value. Negated by using the word not or ~  Let p: I get paid on Friday. Then, ~p: It is not true that I get paid on Friday, or simply “I don’t get paid on Friday”.  Let e:Europe is a city. Therefore ~e: It is not true that Europe is a city, or simply “Europe is not a city”. p~p TF FT

4. TF Statements/Conjunctions Join two TF statements by the word and. The symbol for the conjunction is ^.  Let b: Jordan plays basketball.  Let c: Jordan stars in TV commercials. The conjunction “Jordan plays basketball and stars in TV commercials” is written symbolically as b^c.

5. TF Statements/Disjunctions Join two TF statements by the word or. The symbol for the conjunction is ˅.  Let p: I will pass this CST121.  Let s: I will go to summer school. The disjunction “I will pass this CST121 or I will go to summer school” is written symbolically as p ˅ s.