1.4.notebook
September 12, 2016
Quiz #3
1) Draw a Venn Diagram to show that this argument is invalid:
1. All dogs are mammals
2. Some animals are mammals
Therefore, some animals are dogs
2) Construct a truth table for the symbolic expression 1
1.4.notebook
September 12, 2016
1.4 More Stuff with Conditionals
The Inverse, Converse, and Contrapositive
"If my computer's wifi isn't working,
"If my computer's wifi IS working, then
then I can't use the WebAssign website."
I CAN use the WebAssign website."
"If I can't use the WebAssign website, then
"If I can use the WebAssign website,
my computer's wifi must not be working."
then my computer's wifi must be working."
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1.4.notebook
September 12, 2016
The "Biconditional"
A triangle has three equal angles if and only if it has three equal sides.
p = a triangle has three equal angles
q = a triangle has three equal sides
p q, which means: (p ⇒q)∧(q⇒p)
p
q
T
T
T
F
F
T
F
F
p q
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1.4.notebook
September 12, 2016
Parentheses
p = I build planter boxes
q = that gopher gets in my garden
r = I will lose my lettuce
(p∨q)⇒r
p∨(q⇒r)
Parentheses are not needed with the negation symbol (~).
Parentheses are not needed when the sentence only uses one kind of symbol (Λ or V ).
Parentheses ARE needed any time there is more than one kind of symbol in the sentence!
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1.4.notebook
September 12, 2016
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