Xuanxuan Qijing Problem 19 / Solution

[Diagram]

Notice this only works because the marked black stones have no outside liberties. W7 puts them under atari and black has no time to play at W9.


Here's some related problems related to basic shapes. The outside liberties are important. All of them are black to play and live.

[Diagram]

Related #1

[Diagram]

Related #2

[Diagram]

Related #3


Solutions

[Diagram]

solution for #1

If black plays 'a' this is revert to the original problems, and it's wrong. The best black can do is B1 here. More information at long L group; it's alive in seki.

[Diagram]

solution for #2

B1 here is correct. 'a' would make black alive too, but only in seki; when black plays B1 the group lives with points.

[Diagram]

solution for #3

In a situation like this the best black can do is get a ko with B1 here. More information at long L group. If you have been looking at this page carefully, it's obvious 'a' doesn't work for black.


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