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Square Nine in the Corner
Path: LifeAndDeath   · Prev: GunEight   · Next: SixDieButEightLive
   

Square nine in the corner is related to the carpenter's square.

1. No outside liberties

[Diagram]
Diag.: Square nine

When there are no outside liberties, White can turn this into sente seki. The vital point (obviously) is 'a'.


[Diagram]
Diag.: Main line

2 and 3 are miai. Black 6 avoids White starting an approach ko at 'a'.

KarlKnechtel: Coincidentally, I was studying this eyespace earlier today with a friend on LGS?...



[Diagram]
Diag.: KK contributes this variation at 6

This way avoids the approach ko as well. Note that black cannot resist white's attempt later by filling the ko in response to the approach:


[Diagram]
Diag.: Oops! (b 6 tenuki)

Now black's eyespace is AlmostFilled with a BulkyFive, and black dies.



[Diagram]
Diag.: Variation at 5

This becomes seki too, but if Black omits 6, the ko started at 6 is slightly more advantageous for Black in that he can capture first.


[Diagram]
Diag.: Variation at 4

Black 4 here is not so good, as it invites a two stage ko?.


[Diagram]
Diag.: Variation at 3

This variation also becomes seki, but White ens in gote.


[Diagram]
Diag.: Variation at 3 (ii)

Black trying to avoid seki by taking away the eye is NO good idea because it becomes seki anyway and Black takes gote too.


2. One outside liberty

[Diagram]
Diag.: Main line

With one outside liberty the same main line applies, except that White must play gote at 7 to make it seki.


3. Two or more outside liberties

[Diagram]
Diag.: Main line

With two or more outside liberties, the attempt to make seki fails. White 1-7 can better be held in reserve as ko-threats.



Path: LifeAndDeath   · Prev: GunEight   · Next: SixDieButEightLive
This is a copy of the living page "Square Nine in the Corner" at Sensei's Library.
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