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Mathematics 15 Online
OpenStudy (happykiddo):

what would be the truth table for ~(p ∨ q) ∧ ~p?

OpenStudy (anonymous):

lets see if i can write a truth table here

OpenStudy (anonymous):

what the heck is a truth table? lol

OpenStudy (happykiddo):

the explanation the class lesson gives is pretty shoddy so help very much needed :D

OpenStudy (anonymous):

ok lets start step by step

OpenStudy (anonymous):

\[\begin{array}{|c|c} P & Q \\ \hline T& T \\ T & F \\ F & T \\ F& F\\ \hline \end{array} \] here is our starting piont, it gives all possible combinations of true and false for the two statemenst p and q

OpenStudy (anonymous):

so far so good?

OpenStudy (happykiddo):

yep i got that far

OpenStudy (anonymous):

now we have a ~p there so lets add that \[ \begin{array}{|c|c|c} P & Q & \lnot{}P \\ \hline T & T & F \\ T & f & T\\ F & T & F \\ F & F & T \\ \hline \end{array}\] we get that by changes all the T to F under P and vice versa with me so far?

OpenStudy (happykiddo):

yep

OpenStudy (anonymous):

now we also see a \(P\lor Q\) so lets add that for that one, all is true unless both P and Q are false

OpenStudy (anonymous):

\[\begin{array}{|c|c|c|c} P & Q & \lnot{}P & P\lor{}Q \\ \hline T & T & F & T \\ T & F & T & T \\ F & T & F & F \\ F & F & T & T \\ \hline \end{array}\]

OpenStudy (happykiddo):

wait a second i thought ~P= F F T T

OpenStudy (anonymous):

yes are right. i was so excited to format the table that i made a mistake good eye

OpenStudy (anonymous):

\[\begin{array}{|c|c|c|c} P & Q & \lnot{}P & P\lor{}Q \\ \hline T & T & F & T \\ T & F & F & T \\ F & T & T & F \\ F & F & T & T \\ \hline \end{array}\]

OpenStudy (anonymous):

that's better

OpenStudy (anonymous):

next line. we need \(\lnot(P\lor Q)\) so we change all the T to F and vice versa under the line \(P\lor Q\)

OpenStudy (anonymous):

don't worry, only one more to go

OpenStudy (anonymous):

\[\begin{array}{|c|c|c|c|c} P & Q & \lnot{}P & P\lor{}Q & \lnot{}(P\lor{}Q) \\ \hline T & T & F & T & F \\ T & F & F & T & F \\ F & T & T & F & T \\ F & F & T & T & F \\ \hline \end{array}\]

OpenStudy (happykiddo):

I thought PvQ was....T T T F

OpenStudy (anonymous):

let me know if you have any questions thus far one more and we are done

OpenStudy (anonymous):

\[\begin{array}{|c|c|c|c|c} P & Q & \lnot{}P & P\lor{}Q & \lnot{}(P\lor{}Q) \\ \hline T & T & F & T & F \\ T & F & F & T & F \\ F & T & T & T & F \\ F & F & T & F & T \\ \hline \end{array}\]

OpenStudy (anonymous):

well you caught me again. i wasn't thinking, so i guess you know more than you think on this subject

OpenStudy (anonymous):

and more than me at this late hour. but now we are good to go right? because last line is all we need, namely \(\lnot(p\lor q)\land \lnot p\)

OpenStudy (happykiddo):

Well i kinda only need help with the last one the ~(p ∨ q) ∧ ~p :)

OpenStudy (anonymous):

ok well that is it. we only look at the lines \(\lnot(p\lor q)\) and the line \(\lnot p\) and

OpenStudy (anonymous):

and the \(\land\) between them means you only get T if both are T

OpenStudy (happykiddo):

but its V

OpenStudy (anonymous):

\[\begin{array}{|c|c|c|c|c|c} P & Q & \lnot{}P & P\lor{}Q & \lnot{}(P\lor{}Q) & \lnot{}(P\lor{}Q)\land{}\lnot{}P \\ \hline T & T & F & T & F & F \\ T & F & F & T & F & F \\ F & T & T & T & F & F \\ F & F & T & F & T & T \\ \hline \end{array}\]

OpenStudy (happykiddo):

oh nevermind gotcha

OpenStudy (anonymous):

if you ever want to generate a nice truth table via the web, and don't mind the fact that they use zeros and ones instead of t and f and write them backwards (zeros first, ones second) try here http://www.kwi.dk/projects/php/truthtable/?

OpenStudy (happykiddo):

oh thanks a bunch your a real hombre :D

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