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Clement
Joined: 24 Apr 2006
Posts: 1111
Location: Dar es Salaam Tanzania
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 Posted: Sat Aug 21, 2021 10:51 am Post subject: Aug 21 VH |
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| Code: |
+-----------------+----------------------+------------------+
| 8 3 45 | 245 245 7 | 9 1 6 |
| 9 7 45 | 6 1458 124 | 3 24 28 |
| 2 1 6 | 9 8-4 3 | 78 a47 5 |
+-----------------+----------------------+------------------+
| 7 2 9 | 3 6 5 | 4 8 1 |
| 6 8 1 | 24 9 24 | 5 3 7 |
| 5 4 3 | 1 7 8 | 2 6 9 |
+-----------------+----------------------+------------------+
| 3 5 8 | 7 12 12 | 6 9 4 |
| 14 9 7 | 45 3 6 | 18 25 28 |
| 14 6 2 | 8 c45 9 | 17 b57 3 |
+-----------------+----------------------+------------------+
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XY-Wing pivoted in r9c8: (4=7)r3c8 - (7=5)r9c8 - (5=4)r9c5 => - 4r3c5; stte |
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Mogulmeister
Joined: 03 May 2007
Posts: 1151
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| Posted: Tue Aug 24, 2021 8:40 am Post subject: Extended pincers |
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Nice one Clement.
Sometimes when you are looking at a puzzle for XY wings you find one but it doesn't make any eliminations.
There is also a 2,4,5 XY Wing at r28c8 and r8c4.
As it stands, no eliminations can be made because the pincers at r2c8 and r8c4 point to r2c4 which is a solved square (6).
No need to abandon these "dead" XY Wings straightaway. See if the pincers can be extended.
In this case the pincers are for 4 but if you extend r2c8 across to r2c3 then that 4 becomes a pincer for 5. Do the same r8c4 => r9c5 also becomes 5.
You now have pincers for 5 at r2c3 and r9c5 which eliminates 5 at r2c5.
On this occasion, this doesn't solve the whole puzzle but is a useful technique when working with XY wings. |
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