MyWikiBiz, Author Your Legacy — Tuesday December 02, 2025
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482 bytes added
, 18:24, 30 April 2009
| Line 3,917: |
Line 3,917: |
| | \\[6pt] | | \\[6pt] |
| | & = & | | & = & |
| − | \{ (x, y) \in L : x = u \} | + | \{ (u, y) \in L \} |
| | \\[6pt] | | \\[6pt] |
| | & = & | | & = & |
| Line 3,927: |
Line 3,927: |
| | \\[6pt] | | \\[6pt] |
| | & = & | | & = & |
| − | \{ (x, y) \in L : y = v \} | + | \{ (x, v) \in L \} |
| | \\[6pt] | | \\[6pt] |
| | & = & | | & = & |
| | \text{the set of all ordered pairs in}~ L ~\text{incident with}~ v \in Y. | | \text{the set of all ordered pairs in}~ L ~\text{incident with}~ v \in Y. |
| | + | \end{array}</math> |
| | + | |} |
| | + | |
| | + | The following definitions are also useful: |
| | + | |
| | + | {| align="center" cellspacing="6" width="90%" |
| | + | | |
| | + | <math>\begin{array}{lll} |
| | + | u \cdot L |
| | + | & = & |
| | + | \operatorname{proj}_2 (u \star L) |
| | + | \\[6pt] |
| | + | & = & |
| | + | \{ y \in Y : (u, y) \in L \} |
| | + | \\[6pt] |
| | + | & = & |
| | + | \text{the elements of}~ Y ~\text{that are}~ L\text{-related to}~ u. |
| | + | \\[9pt] |
| | + | L \cdot v |
| | + | & = & |
| | + | \operatorname{proj}_1 (L \star v) |
| | + | \\[6pt] |
| | + | & = & |
| | + | \{ x \in X : (x, v) \in L \} |
| | + | \\[6pt] |
| | + | & = & |
| | + | \text{the elements of}~ X ~\text{that are}~ L\text{-related to}~ v. |
| | \end{array}</math> | | \end{array}</math> |
| | |} | | |} |