RTG Problem 12 / Attempts

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Mef: I think black is dead

[Diagram]

First instinct


The 1-2 point doesn't look like it will make Black 2 eyes, so lets try something else:

[Diagram]

Alternative A


After W4 Black's second eye has collapsed

[Diagram]

Alternative B


Black doesn't have enough time to save both eyes here, so white will take one either with W4 or by playing W3 should black neglect it.

[Diagram]

One last try


W2 is forced, because black will immediately live by playing it. A, B and C all look miai to keep black dead

[Diagram]

Another chance


Shaydwyrm: B1 here is another interesting move I considered, but it looks like W2 kills.

[Diagram]

Follow up


B3 is strong resistance, but after W6 black is faced with a shortage of liberties.


[Diagram]

Follow up


Willerz: B3 above is wrong -- this B3 makes a and b miai -- Black a makes 2 eyes. Black b makes a seki. So Black can live. White can kill by starting at a.

[Diagram]

White 2 at A


Shaydwyrm: W2 is incorrect, B3 leaves white with no followup.

[Diagram]

Not seki


Shaydwyrm: This is not seki. White can fill black's outside liberties and then play A & B to put black in atari.


[Diagram]

Corrected follow-up


Willerz: Shaydwyrm is right, however I think this B3 makes a and b miai. So Black can live. White can kill by starting at a.

Shaydwyrm: Check the diagram labeled "White 2 at A" above for why white can't kill by starting at A.

[Diagram]

Corrected follow-up follow-up


Shaydwyrm: Aha, but I have considered this as well! W6 forces B7 (in a sense, though black should really tenuki instead of all of these since he's dead), and then the situation is the same as the not-seki above.

[Diagram]

This way?

And if Black replies here?

WillerZ: White a and we're back to where we were just now.


[Diagram]

How about this?


unkx80: Referring to Alternative A, how is this?

[Diagram]

Black has a ko?


Shaydwyrm: Looks like black has a 2 step ko, since he needs an approach move at a. He should not play his approach move at b, since that gives white a local threat at c. White can play W4 at B5, then black W6, white b, black c for a seki if black is komaster.[1]

[Diagram]

Black has a ko?

WillerZ: Doesn't this W6 (instead of a) give White a better result? Also, I am not sure that this W4 is the best W4.
Shaydwyrm: This is not a better result, since black next plays b and has a direct ko instead of a 2 step ko. However, it seems you're right that W4 is not the best, see below.

[Diagram]

Also ko


Shaydwyrm: W2 here also leads to ko, but it is direct.


[1]

[Diagram]

Seki?

Nando: Shaydwyrm, this doesn't look like seki to me...
Shaydwyrm: ...you're absolutely right, I guess B3 doesn't help black after all. B5 at W8 is met with W6 at B5. So all the ko discussion above is merely academic, how disappointing...

unkx80: Unfortunately yeah... there is no ko here.


This is a copy of the living page "RTG Problem 12 / Attempts" at Sensei's Library.
(OC) 2004 the Authors, published under the OpenContent License V1.0.
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