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[go]$$c Lee Changho life and death, v.6, problem 6, black to play
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$$ | X X X X X . . . X .
$$ | O O O O X . X X O O
$$ | . X X O X X O O . .
$$ | . . . O X O . . O .
$$ | . . . . O . . . . .
$$ ----------------------[/go]

the problem is from this series.
I think the answer given in the book is wrong. I'll post the solution from the book in hide tags in case anyone wants to solve it themselves before looking at the answer.

The book's answer:

Or is there something I'm missing?

Unfortunately the answer I came up with myself doesn't work as I figured out while writing this post.

After either a or b, black can play G1, and white won't be able to save the three stones in atari due to damezumari.

Yeah, I saw that but it's better than the whole thing dieing or letting black live in the corner isn't it? Black also has to capture in gote.

Black gets gote regardless, so we can ignore that.

In the book solution, black gets two points in the corner, while white gets 8 point on the bottom inside the diagram (and probably more outside it).

In the damezumari solution, white gets 10 points in the corner, while black gets three stones and damages the lower side. In the endgame, H2-J1 will be sente for black, with risk of ko if white blocks (though the situation is complex, due to the possible snapback that lingers around F2). Maybe white will gain a few points, maybe not. Which way is better depends on how the lower side is. If it can become weak, then being split is worse than letting black live in the corner.

Either solution is sufficiently successful for black, IMO. The key to the problem is finding the aji in the corner with the throw-in and the resulting life or ko or capture.

Ok. So white's optimal play would be partially dependent on the rest of the board. Thanks for your help.

In Tsume-Go, you are usually asked to find the sequence that gives the strongest resistance.

This will not necessarily be the sequence you would play in a real game.

In the problem shown, White's strongest resistance ends in Ko. In a real game - dependant on the surrounding position - it might be advisable to let Black live in the corner unconditionally.

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The really most difficult Go problem ever: https://igohatsuyoron120.de/index.htm
Igo Hatsuyōron #120 (really solved by KataGo)