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Capturing Race Exercise 8 Solution
    Keywords: Problem

[Diagram]
Black first.

If Black first, playing at 1 captures the two white stones and the question is over.



[Diagram]
White first.

It is more interesting when White plays first. White 1 ataris to increase the liberties, followed by the hane at 3 to prevent Black from making two eyes in the corner. Note that White can throw in at a any time, so the eye at a has effectively only one liberty.


[Diagram]
White first.

The correct move is Black 4, which may be a blind spot for some. It prevents White from creating a ko there. Up to Black 8, White is unable to make the approach move at a due to a shortage of liberties. This is a typical case of a capturing race where the group that has an eye kills a group that has no eye.


[Diagram]
Variation.

White 5 and 7 here are tricky: it actually attempts to make a seki. The throw in at 8 destroys the possibility of White making an eye there, and is the only correct move. If White 7 is played at 8, Black will play at 7.



[Diagram]
Failure.

Reducing White's liberties directly at 4 in this diagram is wrong. White makes two throw ins at 5 and 7, and fights a big ko in the corner.



Conclusion: The two marked White stones in the question are dead.



This is a copy of the living page "Capturing Race Exercise 8 Solution" at Sensei's Library.
(OC) 2003 the Authors, published under the OpenContent License V1.0.