Question

I'm just trying to read my question (one symbol I don't get in there).

Answer 1

where is it? @idku

Answer 2

I am given a "claim" to examine, and the claim is as follows:

\({\rm For~all~non-empty~relations}~R~{\rm~from}~A~{\rm~to}~B~\\{\rm (with}~A~{\rm and}~B~{\rm being~non-empty~sets),}~~\color{blue}{R^{-1}~\circ~~R~\subseteq~I_A}.\)

Answer 3

I know what relations are, and know what their inverses are as well (at least roughly), all I need to know is what does \(I_A\) come to denote?

Answer 4

I would guess the "identity" value e.g. in multiplication, 1

Answer 5

I think I found my notations (in a slightly harder content than mine, but I think I found it).

Source: http://mathhelpboards.com/discrete-mathematics-set-theory-logic-15/order-i_a-13802.html

Answer 6

Like, if \(A=\{\ell,~\beta,~\omega\}\), then

\(I_A=\{ \langle \ell,\ell \rangle,~\langle \beta,\beta \rangle,~\langle \omega,\omega \rangle \}\)

Answer 7

but, why do they use \(\langle \rangle\) and not \(()\) ?