XuanxuanQijingProblem307/Solution

Table of contents Table of diagrams
Solution: W makes a favorable ko
W3 would be wrong
Wrong defense by B. (W7 at W3)
Wrong attack by W #1
Wrong attack by W #2 (W7 at BB)
W5 would be wrong.
B4 would be wrong.
W3 would be wrong.
B2 would be wrong.
B2 would be wrong. (W7 at BB)
B2 would be wrong.
Altered Situation #1
Altered Situation #2
Altered Situation #3

Correct sequence

[Diagram]

Solution: W makes a favorable ko

W1 is the only first move. W takes the ko first here and has a local threat at the marked location. B2 being the only move for B.

Reasoning

[Diagram]

W3 would be wrong

Would result in a miai.

[Diagram]

Wrong defense by B. (W7 at W3)

If W is allowed to get W3, B can't get two eyes.

[Diagram]

Wrong attack by W #1

Black can live unconditionally like this (or capture W1 and the solution sequence follows only W1 lost the local threat).


Slightly more complex but wrong attack by W

[Diagram]

Wrong attack by W #2 (W7 at black+circle)

This is the best for both if W1 is played, B takes the ko first here as opposed to the correct solution where W does.

[Diagram]

W5 would be wrong.

Alive thanks to the miai.

[Diagram]

B4 would be wrong.

W would take the ko first here (notice this is a direct ko).

[Diagram]

W3 would be wrong.

Wrong due to the same miai.

[Diagram]

B2 would be wrong.

Would revert to the previous direct ko where W takes first.

[Diagram]

B2 would be wrong. (W7 at black+circle)

Back to the ko which B takes first.

[Diagram]

B2 would be wrong.

Dead.

Bonus Comment - Altered Situations

[Diagram]

Altered Situation #1

How do you think the change affect the best sequence?

[Diagram]

Altered Situation #2

And here?

[Diagram]

Altered Situation #3

What can W gain here?


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