Gokyo Shumyo, Section 1, Problem 26 / Solution

Solution

[Diagram]

Main line

The tesuji here is W3. After W9, Black can't create a dead shape with a, because he is in shortage of liberties (this is oshitsubushi). Note what a difference a black stone on the marked point would make.

[Diagram]

Variation 1

White has to be careful to answer B4 at W5 and not at W7. The strength of B3 is precisely that it already prevents the connection underneath.

[Diagram]

Variation 2

Answering B4 at W5 is the only move. It appears as if White can destroy the eye after this sequence by throwing in again at B8, but White will simply connect at a.

[Diagram]

Variation 3

After W5, a and b are miai. (If Black tries to leave White with a big eye by connecting at a (almost filling the enclosed space with the dead shape of three in a line), White runs to b and gets a second eye at c.)

[Diagram]

Variation 3b

B2 here is met by W3 with similar variations.

[Diagram]

Variation 4

After W1, B2 doesn't work, as is shown by this diagram. After W5, a and b are miai.


Failures

There are many ways for White to go wrong. Let's assume she takes W1 as the obvious move, but fails to see the tesuji of W3 in the main line.

[Diagram]

Wrong 1

Black's hane produces a ko.


[Diagram]

Wrong 2

Black kills with the same hane.

[Diagram]

Wrong 2


[Diagram]

Wrong 3

Simple descent of W1 is essentially the same as Wrong 2.


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