Gokyo Shumyo, Section 1, Problem 57 / Solution

Solutions

[Diagram]

Traditional Solution

W1 threatens a double atari at B2, in which case White escapes. Next White occupies the vital point at B3. In terms of life and death, the points a and b are now miai, while the circled point provides an eye.

[Diagram]

Alternative Solution

W3 here also lives. a and b are miai.

(The exchange White b and Black c does not affect the solutions. The resulting shape is a notcher with code 213WN.)


Failures

[Diagram]

Failure at 3

For someone familiar with notchers, it is clear that W1 is not the correct way to make the group live. B2 becomes the vital point.

[Diagram]

Failure at 1

This W1 fails: Black takes the vital point and reduces the shape to six on the second line? which is dead. (Incidentally, if we make the exchange White a - Black b, this is a notcher of code 123NN with the same result.)

[Diagram]

Variation at 2 (escape variation A)

If Black permits the double atari, after White 7 at the marked stone, he faces either the capture at a or the escape at b.

[Diagram]

Variation at 2 (escape variation B)

Black could answer the double atari W3 with B4. White gets out in this variation, but Black can still attack later on, perhaps with a.


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