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1. The symbol for summation is capital sigma.
2. The backwards E for "there exists" is not an epsilon or any other Greek letter! A sort of epsilon looking character is used for "belongs to" (as in "x belongs to the real numbers").
I have gucharmap installed (this is on Slackware though) and the backwards E is under Latin, but I don't know which font packages are needed to display it. Hmm, one thing I can't find is the upside-down A for "for all".
As you can't seem to understand, he is not talking about the set membership relation (which does not actuall use epsilon, but is pretty close), but about the existence property, whose symbol is a backwards capital latin E without any serifs (and which you can access in latex with "/exists"). This symbol is widely-used in mathematical literature (especially in first-order-logic) where it represents existence quantification (as opposed to universal or unique quantification).
(The following statements hold, provided you have a correctly-configured web browser and the appropriate fonts) It should look something like this: ∃
Epsilon (capital and lowercase) look like this: Ε ε
Set membership, which you seem to know about looks like this: ∈
A symbol rarely used in common literature is the backwards lowercase epsilon (which denotes “such that” but whose use has been dropped in favor of that of a colon or vertical bar), which looks like this: ∍