How do you evaluate $\bigcup\bigcup S$ if $S = \{\{a\},\{a,b\}\}$? How do you evaluate $\bigcup\bigcup S$ if $S = \{\{a\},\{a,b\}\}$? I understand that $\bigcup S = \{a,b\}$ but how can I find $\bigcup\{a,b\}$ if I don't even know what the elements of $a$ and $b$ are? Here is a picture of the exercise from the book I saw this in
$S$ has only two elements $\{a\}$ and $\{a,b\}.$ The double union of $S$ is still $S$ itself. It is NOT $\{a,b\}$
$S$ has only two elements $\{a\}$ and $\{a,b\}.$ The double union of $S$ is still $S$ itself. It is NOT $\{a,b\}$