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Beginner Exercise 86 Solution
The result is a ko. Refer to Tripod group. Discussion
Paul Pogonyshev: this move looks fine. It threatens squared stones. lavalyn: not really. See below Paul Pogonyshev: yes, it's not that fine it looked :)
If white captures, black responds with 5.
If white doesn't capture again, he loses the squared stone and second eye. So he has to play at 6. Black threatens with 7. White has no option other than to connect with 8 and then black captures ko with 9, forcing white to connect with 10. It's over now: black places a stone at a, killing white.
unkx80: White 4 in the above dagram is OK, but white 8 is wrong. White 8 should simply capture a stone in the corner and make two eyes at 10. Of course, lavalyn's alternative way of playing white 4 (shown below) is correct too. lavalyn claims the solution above fails:
Delaying the capture but preventing Black from playing in the corner - no suicide allowed.
The exchange of 3 for 4 is necessary to reduce the White liberties. Now when the ko is played at 5, White must take - unlike the previous diagram. Paul Pogonyshev: it's night and i am tired, but as i can see, white is strongly alive with three eyes here. What's wrong? lavalyn: 4 and the two labelled White stones are in atari. But if White fills the atari, Black takes the corner - the resulting 3-space nakade is dead.
Paul Pogonyshev: this is what i believe is on the board after the sixth move. Black can't capture at a due to ko-rule. Next move (8) white captures at b, or if black has played there, at c and lives with three eyes. Or no? unkx80: Please see Basic Kofight Example on what goes on during a ko. Paul Pogonyshev: ok, i knew what ko is ;) I merely misunderstood the task, thinking it was to kill white.
This looks like it also works for ko. However, since White captures first on the previous diagram, White will prefer playing 4 directly beside 3. For more information, reference the Tripod Group.
This is a copy of the living page "Beginner Exercise 86 Solution" at Sensei's Library. (C) the Authors, published under the OpenContent License V1.0. |