We will award partial credit if you do a proof with an out-of-bounds rule, (i.e. use ana con when we told you not to) We will also award partial credit if you turn in an informal write up arguing why you thought the argument is valid/invalid. The only way to get full credit is to do all the proofs in fitch and stay within the restrictions for each problem.
Fitch seems to be acting up on the Macs... So if you have several steps missing in your printout of the long proofs, just write them in by hand. Please make sure to include the rules and the lines the rules apply to. Please don't handwrite your entire proof from Fitch, try to print and fill in the missing lines.
Question 1. Part b. If you want to prove this, use fitch. no taut con, ana con or FO con. If you think you want to disprove this, you can use Tarski's World (assign predicates to the variables) or just explain it.
Question 3:
Please document your assumptions briefly if there is any confusion. We'll take your just justification into account when grading your exam.
You are restricted to the predicates that we give you.
if someone sends/receives email, you can assume he/she has an email account.
You can add another variable if you want.
Please use the form we discuss and use in lecture. Not the shortened form on Page 370.
use of "=" is fine; you don't have to use quantifiers but you have to be careful that "some" does not translate to a specific object...
3b. Assume everyone in the class has an email account.
When we say everyone. We mean including yourself.
3c. when we say other than, we mean someone else in the class.
3f. when we say exactly two, we mean two, no more no less.
4a. By Demorgan's, we mean the strict definition of demorgan's only. On ~ and ^, v. Demorgan's is not defined for conditionals, so you can't use de morgan's law to change the conditionals.
you can use v ^ ~ -> etc. intro, elim all you want
no Ana Con for this problem