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#### bergausstein

##### Active member

- Jul 30, 2013

- 191

Use Venn diagrams to illustrate the following.

a. $\displaystyle A\cup B\,=\,A$ if and only if $\displaystyle B\subset A$

b. $\displaystyle A\cap B\,=\,B$ if and only if $\displaystyle B\subset A$

c. $\displaystyle B\subset A$ if and only if $\displaystyle A'\subset B'$

d. $\displaystyle \left(A'\right)'\,=\,A$

my answers