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This is a continuation from December 2004's problem.
Black is trying to kill the white stone on the 2-1 point. We have now reached the position in Dia 1, which is one which frequently occurs in real games, albeit usually with other stones to collide into further along the edge. Here I ask what happens - White to play - on an other wise empty board.
Dia 2 shows White living. It makes no difference if Black throws in atariing the 1st line connection stones. White gets one eye in the corner and a second towards the bottom of the right side. Additionally White is "out" down there.
Note that twice black jumps one point to try to get ahead of white, but white's pushes force: An initial extension by Black else he has too many immediate cutting points; Then a hane to prevent four in a row which would also make an eye. The resulting black cutting points are a sufficient headache to allow this white life.
Note also that this is the answer to a very specific question - can the White group live. It does not mean that this is sensible play - Black has developed enormous influence to the left and this would be fatal in a real game of Go.
Now although this wasn't part of January's question, I'm also reviewing alternate Blacks 5' in Dia 3.
Dia 4 is exactly the same pattern - just a different sequence.
Dia 5 is the same pattern extended down the right one further - the cutting sequence still applies.
Dia 6 is an equivalent pattern and the cutting sequence still applies.
Dia 7 shows what happens if Black tries a different 7'. White either catches the two central black stones in a ladder or the two right side stones in a net.
In all the cases White lives. Thus I conclude that White at the 2-1 point cannot be killed. Note that this has not been an exhaustive analysis, so if you prove me wrong, please let me know.)
There is no February 2005 problem.
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Last updated 2005-03-06
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