That move is incorrect. The corner is actually ko for life.
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| Kill corner? http://prod.lifein19x19.com/viewtopic.php?f=15&t=10392 |
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| Author: | Aidoneus [ Tue Jun 03, 2014 10:05 am ] |
| Post subject: | Kill corner? |
Can Black kill this corner with my first move? Or maybe Bc1 not the key move? Here is my read, mistakes and all. 1) If Wf1 (?) Bd1, forcing Wd2 then Bb2 threats to link out and WA2 or WA3 allows Black to play Bc2 followed by Bb1 to make bulky five, right? 2) If Wd1 Bc2 kills, right? 3) If Wc2 Bd1: then a) We1 (?) Ba3, Wa2 Bb1 kills, I think; but b) Wb1 lives, as far as I can tell, so I'm stuck here. Is Bd1 a mistake? |
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| Author: | DrStraw [ Tue Jun 03, 2014 10:31 am ] |
| Post subject: | Re: Kill corner? |
There is a much easier way to approach this. The L+1 group lives or dies with sente. That means that in response to a white cannot play b and must play c. But then after d white cannot block, otherwise e kills. So, the two statements: 1. L+1 is sente. 2. After d the tesuji is e. will, between them, pretty much answer all questions regarding this position. Of course, there are other moves to look at, but if you know these two things then everything becomes simple. |
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| Author: | Uberdude [ Tue Jun 03, 2014 10:45 am ] |
| Post subject: | Re: Kill corner? |
A general piece of advice for how to approach tsumego. Start by playing from the outside to reduce the eyespace ("there is death in the hane"). Only after you have shown that doesn't work think about playing inside moves first. |
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| Author: | moyoaji [ Tue Jun 03, 2014 10:54 am ] | ||
| Post subject: | Re: Kill corner? | ||
That move is incorrect. The corner is actually ko for life.
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| Author: | Aidoneus [ Tue Jun 03, 2014 10:55 am ] |
| Post subject: | Re: Kill corner? |
I started by looking at two hanes, but thought that Wc2 would make two eyes after Bb1--overlooking that Bg1 forces the right eye to be false since White can't protect with We1 because of Bc1. Again, thank you both for the help. The corner tesujis give me so much trouble! |
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| Author: | Aidoneus [ Tue Jun 03, 2014 11:04 am ] |
| Post subject: | Re: Kill corner? |
moyoaji wrote: That move is incorrect. The corner is actually ko for life. No, DrStraw is right. Bb1 is a nice killing tesuji! |
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| Author: | moyoaji [ Tue Jun 03, 2014 11:14 am ] |
| Post subject: | Re: Kill corner? |
Are you guys sure this kills? It still looks like ko to me. From what I read of DrStraw's post, he isn't saying that 'e' kills, he says it is a powerful combination after 'd'. Which is true and which is what I posted in my analysis. EDIT: If you are speaking of this variation, here is what I read - |
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| Author: | HermanHiddema [ Tue Jun 03, 2014 11:16 am ] |
| Post subject: | Re: Kill corner? |
After the hane, it is a JGroup, which dies like this: |
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| Author: | moyoaji [ Tue Jun 03, 2014 11:27 am ] |
| Post subject: | Re: Kill corner? |
Right, sorry. I found it.  |
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| Author: | HermanHiddema [ Tue Jun 03, 2014 11:37 am ] |
| Post subject: | Re: Kill corner? |
@moyaji: white should answer  with  immediately, otherwise capturing  is sente and black can get out.
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| Author: | moyoaji [ Tue Jun 03, 2014 11:44 am ] |
| Post subject: | Re: Kill corner? |
HermanHiddema wrote: @moyaji: white should answer with immediately, otherwise capturing is sente and black can get out.If the possibility of getting out is included in this, then why does black not just capture with  so he has enough liberties? Assuming that white has to block in some fashion then the variation at will work after the capture.I do agree, however, that if black plays that white should play as  .
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| Author: | DrStraw [ Tue Jun 03, 2014 11:47 am ] |
| Post subject: | Re: Kill corner? |
moyoaji wrote: From what I read of DrStraw's post, he isn't saying that 'e' kills, Yes I was. It is a standard tesuji which any midkyu needs to know. |
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| Author: | Uberdude [ Tue Jun 03, 2014 11:53 am ] |
| Post subject: | Re: Kill corner? |
HermanHiddema wrote: Sorry to be picky Herman, but it's subtlety different as there are two stones not one at the lower right leg. In this case it doesn't make a difference to the status, but in other cases it can so this approach of simplifying to known corner shapes doesn't always work (though obviously it gives a good idea of things to try). For example: |
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| Author: | moyoaji [ Tue Jun 03, 2014 11:59 am ] |
| Post subject: | Re: Kill corner? |
Uberdude wrote: Sorry to be picky Herman, but it's subtlety different as there are two stones not one at the lower right leg. In this case it doesn't make a difference to the status, but in other cases it can so this approach of simplifying to known corner shapes doesn't always work (though obviously it gives a good idea of things to try). James Davies considers this a J-Group. It's status problem 5 of the J-Group chapter in Life and Death. Page 111 in my copy. DrStraw wrote: Yes I was. It is a standard tesuji which any midkyu needs to know. I see that now. I am sorry. I failed to read one move farther than what I needed to. I did see the tesuji, but I did not see how it would succeed in that case. I was not familiar with this particular life and death problem. |
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| Author: | HermanHiddema [ Tue Jun 03, 2014 12:12 pm ] |
| Post subject: | Re: Kill corner? |
@moyoaji: You can prevent the escape and black still cannot live: After Black is out of options, because a is answered with b, and c is answered with d@Uberdude: I am aware of that, but this is generally considered a J-Group, AFAIK, and is shown as such on the page I linked. |
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| Author: | Aidoneus [ Tue Jun 03, 2014 12:16 pm ] |
| Post subject: | Re: Kill corner? |
moyoaji wrote: I did see the tesuji, but I did not see how it would succeed in that case. I was not familiar with this particular life and death problem. I always tell my math students to not be afraid to ask questions. If one of them needs clarification, there are probably five more students too shy to ask. So, I am glad if others--including those much stronger than me--benefited from my ignorance!  Edit: For those, like me, without Davies' book, you can find the J group discussed at: http://senseis.xmp.net/?JGroup |
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| Author: | Uberdude [ Tue Jun 03, 2014 1:32 pm ] |
| Post subject: | Re: Kill corner? |
Ok yeah, it's a J group in the sense of belonging to the J group family of related shapes. My point was the (basic) J group being dead: doesn't logically imply that this one is: In this case they are both dead with the same killing sequence, but the tripod group extra leg example shows a shape where this change changes the status. I remember being surprised by this in a game. |
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