Five stones on the third line in the corner

   
[Diagram]

Five stones on the third line in the corner

Unlike the case of five stones on the second line in the corner, this White group is unconditionally alive if there are no other stones nearby because it has more eyespace.



1. No other stones nearby

[Diagram]

If black plays first: Case 1-A

The best black can do is to make a small reduction in sente. (B3 can also be played at a, but that gives white an extra ko threat.)



[Diagram]

If black plays first: Case 1-B

Since there are no other stones nearby, Black's attempt to make ko is easily foiled with W4-W6. If B7 connects at a, white ataris from the left. And if black tries to play out the capturing race at playing at b, white ataris at c and puts black into oiotoshi. (There is no ko, because two stones will be in atari after white plays at c.)


2. If black does have a stone nearby

[Diagram]

If the surrounding situation is different...

If Black has an extra stone at a, b, c, or d, and White has no extra stones in the area, the status of white group becomes unsettled.


[Diagram]

If black has a stone at a and sente

If Black has sente and an extra stone at the marked spot, White dies unconditionally, as Black can kill via the Bulky Five shape. Notice that the same position can be reached if White decides to tenuki in Case A above.


[Diagram]

If black has a stone at b and sente

Even if the extra black stone is one line away, Black can still kill. This variation, for example, transposes to the diagram above.


[Diagram]

If black has a stone at c and sente

If the extra black stone is another line farther to the right, black can still kill. (White can capture B3 next, but black then connects at b and there is no second eye).


[Diagram]

If black has a stone at d and sente

And for the same reason, a black stone at d makes the white group killable.



--MrTenuki


This is a copy of the living page "Five stones on the third line in the corner" at Sensei's Library.
(OC) 2007 the Authors, published under the OpenContent License V1.0.
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