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Use ¬, →, ∧ and ∨ to express the following declarative sentences in propositional logic; in each case state what your respective propositional atoms p, q, etc. a) If interest rates go up, share prices go down. b) If Smith has installed central heating, then he has sold his car or he has not paid his mortgage. c) Today it will rain or shine, but not both. d) If Sam met Jane yesterday, they had a cup of coffee together, or they took a walk in the park. e) My sister wants a black and white cat.

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Answer:

a) If interest rates go up, share prices go down : this will be assigned p→q

b) If Smith has installed central heating, then he has sold his car or he has not paid his mortgage. P → (q∨¬r)

c) Today it will rain or shine, but not both:(p∨q) ∨ ¬(p∧q)

d) If Sam met Jane yesterday, they had a cup of coffee together, or they took a walk in the park. P → (q∨r)

e) My sister wants a black and white cat. p∧q

Explanation:

A statement is said to be propositionally logical if the statement that can be assigned either true or false.

∧and

∨or

¬not

→implies

a) If interest rates go up, share prices go down : this will be assigned p→q implies because the occurrence of event (share prices go down) depends on the possibility of the other event happening.

b) If Smith has installed central heating, then he has sold his car or he has not paid his mortgage. P → (q∨¬r) : either of the two of the other events (i.e. he has sold his car or he has not paid his mortgage ) can only occur if the first event occur

c) Today it will rain or shine, but not both:(p∨q) ∨ ¬(p∧q) : either of the events can occur but not both i.e. they are mutually exclusive

d) If Sam met Jane yesterday, they had a cup of coffee together, or they took a walk in the park. P → (q∨r) either of the two of the other events (i.e. they had a cup of coffee together or they took a walk in the park ) can only occur if the first event (Sam met Jane yesterday) occur

e) My sister wants a black and white cat. p∧q : both events can only occur together

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