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Mathematics 12 Online
OpenStudy (anonymous):

Can anybody help me construct a truth table????

terenzreignz (terenzreignz):

I can... but I am limited by the capacity of drawing truth tables here...

OpenStudy (anonymous):

we could do one row at a time if that would be easier because i'm not sure how to draw one on here.

terenzreignz (terenzreignz):

I'll give you the basic framework. First, you know your logical operators right? The "not", "and", "or", "implies" etc?

OpenStudy (anonymous):

yes

terenzreignz (terenzreignz):

Okay... first thing you gotta do is identify the main operator. Now... let's start with the easiest. \[\large \left[\begin{matrix}\neg & P \\ ? & ? \\ ? &?\end{matrix}\right]\] The main operator here is the negation (NOT) operator, right?

OpenStudy (anonymous):

yes

terenzreignz (terenzreignz):

Right. First, pick one of your variables. You only have one, so let's pick P. Under it, write down all possible "truth-values" of P. Truth values just mean either a true or false, 1 or 0, you be the judge. I'll just use T and F. Just tell me if you'd be more comfortable using 1 and 0.

OpenStudy (anonymous):

T and F are fine.

terenzreignz (terenzreignz):

\[\large \left[\begin{matrix}\neg & P \\ ? & \color{green}T \\ ? & \color{red}F\end{matrix}\right]\]

terenzreignz (terenzreignz):

Right? Because P can only be either true or false. Catch me so far?

OpenStudy (anonymous):

yeah!

terenzreignz (terenzreignz):

Now... what does the "not" operator do to "true" values? What about to "false" values?

OpenStudy (anonymous):

makes the true values false, and the false values true?

OpenStudy (anonymous):

do you have any expression for which you have to draw a truth table?

terenzreignz (terenzreignz):

Correct. So, write down the effect of the operator... accordingly. \[\large \left[\begin{matrix}\neg & P \\ \color{red}F & \color{green}T \\ \color{green}T & \color{red}F\end{matrix}\right]\] \[\large \left[\begin{matrix}\neg & P \\ \color{red}F &T \\ \color{green}T & F\end{matrix}\right]\] The column underneath the main operator, that is the result of your truth table.

OpenStudy (anonymous):

oh okay!

terenzreignz (terenzreignz):

Now, let's do another one... which one do you want, AND, OR, or IMPLIES, or what? :)

OpenStudy (anonymous):

so if i give you an example can you help me with it?

terenzreignz (terenzreignz):

Sure. But it might take a while.

OpenStudy (anonymous):

that's fine

terenzreignz (terenzreignz):

Hit me~

terenzreignz (terenzreignz):

You're scaring me... this seems lengthy o.O

OpenStudy (anonymous):

okay, so i can't get the graph to work but in my solution is pvq...

terenzreignz (terenzreignz):

Just draw it. Or type it out to the best of your abilities :D

OpenStudy (anonymous):

the first row is T,T,T,?,? second row is T,T,F,?,? third row is T,F,T,?,?

OpenStudy (anonymous):

i have more rows after this

terenzreignz (terenzreignz):

What was given? I mean, the question, what was it?

terenzreignz (terenzreignz):

Was it just p v q ?

OpenStudy (anonymous):

all those rows are possible values, but you have to give main question..

OpenStudy (anonymous):

probably its not just p v q since 3 columns have T/F values :D

terenzreignz (terenzreignz):

The way I'd work out p v q would involve 3 columns though. Go figure :/

terenzreignz (terenzreignz):

But there are two ?'s on each row, implying five columns... the question, @lexiporter12 ?

OpenStudy (anonymous):

here is what im looking at..

OpenStudy (anonymous):

i think he has 3 variables

OpenStudy (anonymous):

can you see it okay?

terenzreignz (terenzreignz):

okay... it's just p v q after all... Let's put that down... \[\large \left[\begin{matrix}p & \lor & q\\ ? & ? & ? \\ ? & ? & ? \\ ? & ? & ? \\ ? & ? & ?\end{matrix}\right]\]

OpenStudy (anonymous):

what is compound statement? and why do you have r?

OpenStudy (anonymous):

(pvq)vr a compound statement is what is in the parenthesis

terenzreignz (terenzreignz):

tsk...\[\large \left[\begin{matrix}(p & \lor & q) & \lor & r \\ ? & ? & ? & ? & ?\\ ? & ? & ? & ? & ?\\ ? & ? & ? & ? & ?\\ ? & ? & ? & ? & ?\\ ? & ? & ? & ? & ?\\ ? & ? & ? & ? & ?\\ ? & ? & ? & ? & ?\\ ? & ? & ? & ? & ?\end{matrix}\right]\]

terenzreignz (terenzreignz):

Ready to proceed, @lexiporter12 ?

OpenStudy (anonymous):

yes

terenzreignz (terenzreignz):

Now, the main operator of your compound statement is this \[\large \left[\begin{matrix}(p & \boxed\lor & q) & \lor & r \\ ? & ? & ? & ? & ?\\ ? & ? & ? & ? & ?\\ ? & ? & ? & ? & ?\\ ? & ? & ? & ? & ?\\ ? & ? & ? & ? & ?\\ ? & ? & ? & ? & ?\\ ? & ? & ? & ? & ?\\ ? & ? & ? & ? & ?\end{matrix}\right]\]

OpenStudy (anonymous):

right!

terenzreignz (terenzreignz):

Scratch that, I think you misunderstood your own question @lexiporter12 The main operator of p v q is this...\[\large \left[\begin{matrix}(p & \boxed\lor & q) & \lor & r \\ ? & ? & ? & ? & ?\\ ? & ? & ? & ? & ?\\ ? & ? & ? & ? & ?\\ ? & ? & ? & ? & ?\\ ? & ? & ? & ? & ?\\ ? & ? & ? & ? & ?\\ ? & ? & ? & ? & ?\\ ? & ? & ? & ? & ?\end{matrix}\right]\] While the main operator of the compound statement is this\[\large \left[\begin{matrix}(p & \lor & q) & \boxed\lor & r \\ ? & ? & ? & ? & ?\\ ? & ? & ? & ? & ?\\ ? & ? & ? & ? & ?\\ ? & ? & ? & ? & ?\\ ? & ? & ? & ? & ?\\ ? & ? & ? & ? & ?\\ ? & ? & ? & ? & ?\\ ? & ? & ? & ? & ?\end{matrix}\right]\]

OpenStudy (anonymous):

ohh okay

terenzreignz (terenzreignz):

so pick a variable... you can pick any variable you want, as long as it's p

OpenStudy (anonymous):

well my chart already tells me what the first 3 columns are, so i just need to find the last two

terenzreignz (terenzreignz):

So under the variable p, divide the column into two halves, the first half being TRUE, the second half being FALSE \[\large \left[\begin{matrix}(p & \lor & q) & \lor & r \\ \color{green}T & ? & ? & ? & ?\\ \color{green}T & ? & ? & ? & ?\\ \color{green}T & ? & ? & ? & ?\\ \color{green}T & ? & ? & ? & ?\\ \color{red}F & ? & ? & ? & ?\\ \color{red}F & ? & ? & ? & ?\\ \color{red}F & ? & ? & ? & ?\\ \color{red}F & ? & ? & ? & ?\end{matrix}\right]\]

OpenStudy (anonymous):

okay got that

terenzreignz (terenzreignz):

No... you will learn to do this from scratch, @lexiporter12 for your own good :D

OpenStudy (anonymous):

haha okay

OpenStudy (anonymous):

the 2nd column would be TTFFTTFF

terenzreignz (terenzreignz):

second colum or the column under q.

OpenStudy (anonymous):

under q

terenzreignz (terenzreignz):

\[\large \left[\begin{matrix}(p & \lor & q) & \lor & r \\ \color{green}T & ? & \color{green}T & ? & ?\\ \color{green}T & ? & \color{green}T & ? & ?\\ \color{green}T & ? & \color{red}F & ? & ?\\ \color{green}T & ? & \color{red}F & ? & ?\\ \color{red}F & ? & \color{green}T & ? & ?\\ \color{red}F & ? & \color{green}T & ? & ?\\ \color{red}F & ? & \color{red}F & ? & ?\\ \color{red}F & ? & \color{red}F & ? & ?\end{matrix}\right]\]

terenzreignz (terenzreignz):

You can also put the values for r... what would they look like?

OpenStudy (anonymous):

TFTFTFTF for r

terenzreignz (terenzreignz):

You see the pattern, right? Alternating T's and F's, but faster alternations every time.\[\large \left[\begin{matrix}(p & \lor & q) & \lor & r \\ \color{green}T & ? & \color{green}T & ? & \color{green}T\\ \color{green}T & ? & \color{green}T & ? & \color{red}F\\ \color{green}T & ? & \color{red}F & ? & \color{green}T\\ \color{green}T & ? & \color{red}F & ? & \color{red}F\\ \color{red}F & ? & \color{green}T & ? & \color{green}T\\ \color{red}F & ? & \color{green}T & ? & \color{red}F\\ \color{red}F & ? & \color{red}F & ? & \color{green}T\\ \color{red}F & ? & \color{red}F & ? & \color{red}F\end{matrix}\right]\]

OpenStudy (anonymous):

right

terenzreignz (terenzreignz):

So... what does the v (OR) operator do to two truth values?

OpenStudy (anonymous):

make them F

terenzreignz (terenzreignz):

No. The v (OR) operator would be true if AT LEAST ONE of the two values it works with are true. That's why I needed to draw another truth table... \[\large \left[\begin{matrix}P & \boxed\lor &Q\\ \color{blue}T & \boxed{\color{green}T} & \color{blue}T \\ \color{blue}T & \boxed{\color{green}T} & \color{orange}F\\ \color{orange}F & \boxed{\color{green}T} & \color{blue}T\\ \color{orange}F & \boxed{\color{red}F} & \color{orange}F\end{matrix}\right]\]

terenzreignz (terenzreignz):

So... can you finish up the second column?

terenzreignz (terenzreignz):

Remember, under the v (OR) operator, you would put a T if there is a T on the left OR a T on the right.

OpenStudy (anonymous):

FFTTT

terenzreignz (terenzreignz):

There are 8 of them...

OpenStudy (anonymous):

TTTFFFTT

terenzreignz (terenzreignz):

NO. I told you, if there is at least ONE true value between the two variables (in this case p and q) it would make the value of the v (OR) operator true. For example, in the first row, you have both p and q as T. Therefore, the value of the v (OR) operator on that row is T.

OpenStudy (anonymous):

TTTTTTFF

terenzreignz (terenzreignz):

That's much better. And those are the truth values of your statement p v q.

OpenStudy (anonymous):

okay so what about the compound statements

terenzreignz (terenzreignz):

\[\large \left[\begin{matrix}(p & \lor & q) & \lor & r \\ \color{green}T & \color{green}T & \color{green}T & ? & \color{green}T\\ \color{green}T & \color{green}T& \color{green}T & ? & \color{red}F\\ \color{green}T & \color{green}T & \color{red}F & ? & \color{green}T\\ \color{green}T & \color{green}T & \color{red}F & ? & \color{red}F\\ \color{red}F & \color{green}T & \color{green}T & ? & \color{green}T\\ \color{red}F & \color{green}T & \color{green}T & ? & \color{red}F\\ \color{red}F & \color{red}F & \color{red}F & ? & \color{green}T\\ \color{red}F & \color{red}F & \color{red}F & ? & \color{red}F\end{matrix}\right]\]

terenzreignz (terenzreignz):

It's the same logic, as with the v (OR) operator, but this time, you compare the truth values of the r-variable to the truth values of the entire pvq statement to the left.

OpenStudy (anonymous):

so if at least one of them is true then it makes the compound statement true?

terenzreignz (terenzreignz):

Yes.

OpenStudy (anonymous):

TTTTTTTF

terenzreignz (terenzreignz):

And that's your answer. Nicely played.

OpenStudy (anonymous):

THANK YUOU

terenzreignz (terenzreignz):

No problem.

terenzreignz (terenzreignz):

I have to go to school now... until the next, guys... ------------------------------------------------ Terence out

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