Math Help - help with proof

1. help with proof

First, I am not sure how to type the correct characters into this message block. I tried character map, but I had no luck. IF anyone wants to tell me if there is a language pack or add-on for this, feel free. Now the proof I am working on is as follows:
prove that $A \subseteq B$ if and only if "the complement of B" $\subseteq$ "the complement of A"

Can someone point me in the right direction? Again any help inputting the symbols is appreciated as well.

2. Originally Posted by totalbs70
First, I am not sure how to type the correct characters into this message block. I tried character map, but I had no luck. IF anyone wants to tell me if there is a language pack or add-on for this, feel free.
Check out this pdf: http://www.mathhelpforum.com/math-he...-tutorial.html

3. Originally Posted by totalbs70
prove that $A \subseteq B$ if and only if "the complement of B" $\subseteq$ "the complement of A"
Notice that $P \to Q\,\, \equiv \,\neg Q \to \neg P$
So $x \in P \to x \in Q\,\, \equiv \,x \notin Q \to x \notin P$