Sets and Logic Flashcards for Discrete Math

Question 1

What do the symbols $\in$ and $
otin$ mean in set notation?

Accepted Answer

$x\in A$ means $x$ is an element of set $A$; $x
otin A$ means $x$ is not an element of $A$.

Question 2

Compute the complement $A^c$ if $U=\{1,2,3,4,5\}$ and $A=\{2,5\}$.

Accepted Answer

$A^c=\{1,3,4\}$.

Question 3

State De Morgan's laws for sets.

Accepted Answer

$$\left(A\cap B\right)^c=A^c\cup B^c,\qquad \left(A\cup B\right)^c=A^c\cap B^c,$$ where complements are taken in the same universal set $U$.

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