Hey there! Sign in to join this conversationNew here? Join for free
x Turn on thread page Beta
    • Thread Starter

    How would you do the lower two questions, with workings shown? (I'm not very good at discrete maths :l)
    Very very grateful for any answers, pointers or help - Thanks in advance

    Part 1
    Establish the inference rule known as constructive dilemma which states that from the two hypotheses (P=>Q and R=>S) and (P or R) we can infer (Q or S).

    [Hint: you will need to construct a truth table with 16 rows]

    Part 2
    Use the rules of inference to show that if A, B, C and D are propositions, the conclusion C or (not D) can be inferred from the four hypotheses , A=>B, B=>(not D), A, B=>C.

    and btw,
    The => symbol was meant to be an arrow symbol (but I couldn't find the keyboard short-cut!) meaning "implies". so (P=>Q) is P implies Q.
    THANKS for any help!!
How are you feeling about your exams?
Useful resources

Make your revision easier


Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here


How to use LaTex

Writing equations the easy way

Student revising

Study habits of A* students

Top tips from students who have already aced their exams

Study Planner

Create your own Study Planner

Never miss a deadline again

Polling station sign

Thinking about a maths degree?

Chat with other maths applicants

Can you help? Study help unanswered threads

Groups associated with this forum:

View associated groups

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.