Gokyo Shumyo, Section 2, Problem 1 / Comments

The following provides some extra material if more than one error is committed in this problem.


Double-Ko Life if White errs twice

[Diagram]

Failure 3: ko??

tderz: White fails.
With a different B2 it looks like ko too.
Black cannot connect at a as b is nakade.
What happens if Black plays at c?
However, see [10] below. White failed twice with W1 and W5.

[Diagram]

Failure 3: double-ko life

tderz: [10] W5 is atari and it looks like ko but, it is life by double ko at b and circle.
Hence, the price for White's two wrong moves (previous W1) and W1 here is, that the status of Black's group deterioated from plain dead over ko with White taking first, to life in double ko (providing at least endless ko threats around 26 points).


Seki

[Diagram]

c) Failure 3: seki

tderz: [70] If thus White continues with W3 here ... B3 lets it end in seki (life).
Black is not fast enough to squeeze with a and c
as White will fill liberties b and d.
See transposition [60] above.


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