Gokyo Shumyo, Section 1, Problem 74 / Solution

Main line: Hashimoto Utaro
Variations: Dieter


[Diagram]
Main line  
[Diagram]
Main line - continuation  

White captures three to make an eye. Black can't protect there because of shortage of liberties.


Variations

[Diagram]
Variation (i) at 8  

If B8 at B1 here, cutting at W2 makes miai of a and b. Note that if White sacrifices just one stone (black+circle at c), it's a ko after B3 at a. :

[Diagram]
Variation (i) at 8 - a  

Capturing at W4 makes a second eye at black+circle. Black can't play B7 at a.

[Diagram]
Variation at 8 - b  

Here too White makes two eyes at the circled points.

[Diagram]
Variation (ii) at 8  

If Black connects at B1, the atari at W2 is sente (see next diagram) and W4 makes a bent four living shape.

[Diagram]
Variation (ii) at 8 - variation  

If B3 here, capturing three stones with W4 assures a quiet life. Even if Black throws in at B5, White is alive with a and b being miai.

[Diagram]
Variation at 4  

Giving atari this way would not be very smart. White now captures either at a or at b.

[Diagram]
Variation at 2  
[Diagram]
Variation at 2 - continuation  

B9 at W6. The variation is long, but up until B1 in this diagram it is forced and the W2-B5 exchange is well known. White has to find the throw-in at W6, though.

[Diagram]
Variation at 2 - variation  

(Black 11 at W8.)

Maybe it is simpler to play W2 here and fire off the sequence W4-B10 then.


Failures

We will have a look at some preparatory moves: why White should not yet start the well-known sequence.

[Diagram]
Failure (i) at 7  

If a has not yet been exchanged for b, White runs out of options. Whatever she does, Black will connect at c.

[Diagram]
Failure (ii) at 7  

Blocking here is not sente: Black can take time to hane. White can't makes an eye in the corner because a and b are miai for Black.

If W3 at b then B4 at a and there are only false eyes in the corner.

[Diagram]
Failure (i) at 5  

The sequence becomes less effective, the more preparatory moves are omitted.

[Diagram]
Failure (ii) at 5  

See previous diagrams.

[Diagram]
Failure: only ko  

If W3 cuts immediately, then White can only achieve a ko and not unconditional life.



Gokyo Shumyo, Section 1, Problem 74 / Solution last edited by hnishy on July 11, 2018 - 14:51
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