Gokyo Shumyo, Section 1, Problem 75 / Solution

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[Diagram]

Main line

By the way, W5 is the famous move Fujiwara-no-Sai immediately spots at a children's tournament in Hikaru no Go chapter 3. See Hikaru problem 1

[Diagram]

Continuation

If Black protects his stone, White captures three to make an eye.


Variations

[Diagram]

Variation at 6

If Black destroys an eye at B1, White surprisingly makes one at W2.

[Diagram]

Variation (ii) at 6

If B3 here, W4 connects and captures because of shortage of liberties.

[Diagram]

Variation (iii) at 6

This way variation (i) still holds its own.

[Diagram]

Variation at 4

Maybe this is a ridiculous variation but I couldn't help wondering what happens when Black takes that marvelous 1-2 point himself.

[Diagram]

Variation at 2

Anyone?

Nando: Well, I gave it a shot and couldn't find a way to unconditional life for White after B2 in this diagram, my best result being ko.

JoelR: After working on this problem a couple of nights and missing some lines, I showed it to my boss, who is 3dan. He was able to finish it off. For now, I'll put the analysis at /Varation.

tasuki: Why exchange 3 for 4? It seems to me that this exchange doesn't help white at all and helps black quite a lot. Why not simply 3 at 5?



By the way Dieter, I totally agree with what you said at the bottom of the tsumego page. I figured a lot of variations starting with that diagram, and although I didn't succeed in solving the problem, I feel that I've learned quite a lot about shape and the special properties of the corner.

Gregory I agree that W3 is a wrong play. W3 must be at W5 (R15) threatening the B6 point at Q14 if Black plays elsewhere.



However, Black may play quite differently from the main line, as follows.

[Diagram]

Variation at 2

See /Varation which shows how White survives if Black plays 6 at a.

Gregory The W5 is the variation. W5 should go back to the mainline solution at the 1-2 point of S19.

JoelR: No, if W5 at 'b', then B6 at 'c'. Since unlike the main line, Black does not have a stone at 'a', he can keep White from capturing three to make an eye.

[Diagram]

Variation at 2 continuation

White's next move seems difficult. But there is a lot of aji for White to exploit. Also, the door is open for White's three stones to escape at 'a'.


[Diagram]

Variation at 2 continuation


If White plays W1, Black resists at B2. After W3 it's a ko.

Actually, White has a better move.

[Diagram]

Variation at 2 continuation

White gets a direct ko, and Black has to find the first threat.


Question from JoelR

What if B2@'a'? -JoelR

Incidentally, I almost had a solution where White didn't have to turn at white+circle, but B1 cooks it. Malcolm I don't understand this. "Nearly" had a solution?

[Diagram]

Answer to question

If Black plays B2, White escapes at W3, leaving Black dead in the corner, and with fewer liberties than White's surrounding stones, so White wins the capturing race.



[Diagram]

hallucination ko variation

tderz: I would like to introduce variations about the (un-)equivalency of this immideate W1. What will happen after black connects at a.

After a-f, g and h are miai in a sense that both times Black will be captured.
At first I thought that bG - wH, bI - wJ would be only ko, however Black is already taken off the board after wJ.

tderz: What did I miss , why W1 could be inferior to a cut at b?

[Diagram]

hallucination ko variation


Concusion

The conclusion for this problem: after White plays the first move in the solution (the cut at b34 (Audouard coordinates), then Black has a choice. Either let White live, or make a ko to kill White, in which Black risks the corner.

This page could do with a good edit!


Authors

Main line: HashimotoUtaro
Variations: Dieter, Malcolm



This is a copy of the living page "Gokyo Shumyo, Section 1, Problem 75 / Solution" at Sensei's Library.
(OC) 2011 the Authors, published under the OpenContent License V1.0.
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