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Old Nov 8, 2006, 07:37 PM   #1
Texas04
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Comp Sci HW Help... boolean algebra

Ahh so confused okay these boolean expressions are very confused. I dont plan on copying and these two are not my only problems, im a good kid that does my hw lol

(A+~B+C)(AB+~(AC))
I simplified it a lot but I think i got lost in them somewhere and I can't quite figure out where.

and this one
~(A+B+AB) I got as far as ~A*~B*~A+~B but im not sure if i can multiply the ~A's or not to get one sigle ~A and end up with ~A*~B+~B

the ~() means the negation of the variable within the parenthesis..

Any help would be greatley appreciated!

Thanks!
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Old Nov 8, 2006, 07:53 PM   #2
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Don't really want to do your homework for you, but I will tell you that ~A*~A = ~A. Think of an AND gate with the two inputs tied together. The output is always just going to be the same as the input.

BTW, I didn't check your simplification on that, but at first glance it looks like it's probably right. As for the first one, quite frankly I'm too lazy to do it right now. I should be doing my own Microwave Engineering homework right now anyway...
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Old Nov 8, 2006, 08:04 PM   #3
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thank you very much for your input and I understand good luck on your microwaves? lol lil over the head of a 16 year old
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Old Nov 9, 2006, 02:02 AM   #4
demallien
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Ahhh, now I remember why I did NO CompSci courses...

before university. Such. A. Waste. Of. Time.

Nobody is ever going to ask you to do an expansion like that. Ever. I've worked in hardware design, cryptography, driver design, User Interfaces, Internet comms of all types, and not once have I needed to know how to do expansions/simplifications on boolean algebra. Evaluate boolean expressions, certainly. Determine the correct boolean expression, that's important too. But transform the thing? The ONLY fields where you would ever need to do that these days are graphics engines for 3D games, and physical simulations, both fields requiring large amounts of optimisation of code for good performance. And even there, most transforms will already have been done for you. And if they're not, and if by some bizarre misfortune Mathematica and Matlab can't help you, you do what any self-respecting programmer would do - write a programmer to do it automatically. That way you can't make any dumb errors...

Actually, that's probably not a bad way of answering the question. Write a simple console app that does the transform for you. Give the source code to your teacher as your answer, and see if he gets it ;-) Not only will you learn something useful (text parsing), but you'll avoid wasting your time learning to do something really unimportant.
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Old Nov 9, 2006, 03:32 AM   #5
telecomm
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Quote:
Originally Posted by Texas04 View Post
~(A+B+AB) I got as far as ~A*~B*~A+~B
You've dropped some parentheses here, and they'll affect your answer.

Oh, and understanding boolean algebra may turn out to be really important if you work in computer hardware, study mathematics, study philosophy, or work in some areas of programming (as emphasized in the post above).

Of course, you could write a program to do the transform for you, but then you'd certainly have to understand enough about this stuff to answer your original questions.
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Old Nov 9, 2006, 11:22 AM   #6
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I don't think it's a waste of time either. Understanding basic boolean algebra is very important as fundamental knowledge if you go into any engineering job involving digital design, like processor design for example. I haven't used a lot of the basic math that I learned in elementary, junior high, and high school (long division anyone?), but learning that stuff makes it so you can build on it and learn more complicated/higher-level stuff.
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Old Nov 10, 2006, 01:07 AM   #7
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one of the basic principles of boolean algebra is

a^2 = a


umm other than that just go step by step and try to find the corresponding simplified equation - there's plenty of alternative ways of applying the boolean mathematical laws - experiment, you'll sure to find some kind of simplification sooner or later through this approach.
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Old Dec 15, 2009, 12:23 PM   #8
xor22
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answer with XOR operator.

I know this is an old thread, but here is
an equation that is the same as the
initial one mentioned at the top of this thread.
I arrived at the answer through a list of
answers I created with a C# computer
program that took 12 minutes to run,
so I kind of cheated. Well here is the
equation:
( A xor (not B)) or ( A xor C )

Here is the link to that C# program:
http://mathisfunforum.com/viewtopic.php?id=13293
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