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| This is an extension of Y-Wing or (XY-Wing). John MacLeod defines one as "three cells that contain only 3 different numbers between them, but which fall outside the confines of one row/column/box, with one of the cells (the 'apex' or 'hinge') being able to see the other two; those other two having only one number in common; and the apex having all three numbers as candidates." It follows therefore that one or other of the three cells must contain the common number; and hence any extraneous cell (there can only be two of them!) that "sees" all three cells of the Extended Trio cannot have that number as its true value. |
| It gets its name from the three numbers X, Y and Z that are required in the hinge. The outer cells in the formation will be XZ and YZ, Z being the common number. |
 XYZ-Wing eg 1 |
| In this example the candidate number is 7 and R3C5 is the Hinge. It can see a 1/7 in R2C4 and a 5/7 in R3C8. We can reason this way: If R2C4 contains a 1 then R3C5 and R3C8 become a naked pair of 5/7 - and the naked pair rule applies. Same with R3C8. If that's a 5 then R2C4 and R3C5 become a naked pair of 1/7 each. If any of the three are 7 then 7 is still part of the formation. Any 7 visible to all three cells must be removed, in this case in R3C6. (Note: Turn OFF Y-Wings and Unique Rectangles) |
 XYZ-Wing eg 1: Load Example |
| The second example shows a two XYZ-Wings with a few steps in between. R4C6 is happens to be common to both XYZ-Wings and the candidate in question, number 7, is also common to both. Aligned Pair Exclusion The logic on an XYZ-Wing is completely different and lot simpler than the Aligned Pair Exclusion described below but the funny thing is that XYZ-Wing is a total sub-set of APE. Every XYZ-Wing can be solved by APE (but not vis versa). (Note: Turn OFF Unique Rectangles) |
 XYZ-Wing eg 2: Load Example or : From the Start |
| XYZ-Wing, Example 3 (same puzzle, a few steps further on): |  XYZ-Wing eg 3 |
