# double complement

Discussion in 'Homework Help' started by gateslogic, Aug 25, 2012.

Aug 25, 2012
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Mar 6, 2009
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3. ### WBahn Moderator

Mar 31, 2012
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And if what is tripping you is the concept behind the 'double complement' identity, it just means that if you logically invert something twice you get the original value back. To prove this, make a Truth Table with A, A', and (A')' for all possible values of A (i.e., all two of them) and you should see that A is the same as (A')' for all possible values. Thus, it is an identity.

4. ### Agonche Member

Aug 26, 2011
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In Boolean Algebra, you have only two values, 0 and 1.

Make sure you understand what complement is.
Complement resembles ordinary negation in that it exchanges values.
So...complement of 0=1, complement of 1=0.

If you double complement (invert twice) 0, you get 0.
And if you double complement 1, you get 1. Therefore (A')'=A.

This is a pretty basic thing to understand.

5. ### gateslogic Thread Starter New Member

Aug 25, 2012
2
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Many thanks to everyone for helping me to find the answer.