# How should I remember the rules of logic?

I'm taking a first course in discreet mathematics and there are a lot of new rules/laws to remember.

My question is what is the best way to remember the rules of logic? How would you remember the:

Absorption Laws

The Domination Laws

Identity Laws

Are there any well known mnemonics, like SOHCAHTOA in trigonometry?

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Forget about mnemonics. From this point forward, you should be aiming for understanding, not memorization. If you understand what these laws are saying, you'll be able to remember them. – Arturo Magidin Jan 16 '11 at 4:09
I do agree with Arturo's comment. But let me mention that for me Venn diagrams help a lot: see en.wikipedia.org/wiki/Venn_diagram You can think of the expression $p$ as selecting the collection $S(p)$ of things satisfying $p$. Then you have for instance $S(p \vee q) = S(p) \cup S(q)$ and $S(p \wedge q) = S(p) \cap S(q)$. The three laws you're mentioning are completely obvious once you draw the appropriate diagrams. – t.b. Jan 16 '11 at 5:06
@Theo: Which, in a sense, is about understanding what the laws are saying. (-: – Arturo Magidin Jan 16 '11 at 6:52
Use them and you won't be able for forget them. – Raphael Jan 16 '11 at 10:34
@lampShade: Does your university offer courses in blabbermouth mathematics too? (-: ("Discrete": made up of separate parts; "Discreet": capable of preserving prudent silence). – Arturo Magidin Jan 17 '11 at 23:40

## 1 Answer

Arturo's and Raphael's comments say it all:

Forget about mnemonics. From this point forward, you should be aiming for understanding, not memorization. If you understand what these laws are saying, you'll be able to remember them.

To get to that point of understanding:

Use them and you won't be able [to] forget them.

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