L-group on the 4th line

  Difficulty: Expert   Keywords: Life & Death
L-group on 4th line  

The black group resembles the L-group but it is on the 4th line instead of the 3rd. It also resembles the Carpenter's square for which it is missing a stone at a. The carpenter's square being ko and the L-group being dead, it is no surprise that this group can be killed, while it is not easy at all to find the sequence. Most hasty attempts will end in ko as well.

Realistic situations would probably involve a cut instead of a firm connection, i.e. the white+circle stone being black. Also the white+square stone is important for containing Black.

This analysis is based on the solution by An Younggil in gogameguru's problem 107: [ext] http://gogameguru.com/weekly-go-problems-week-107/.

It is carried out however by applying How to approach a life and death problem. (Panda Sensei analysis was later added as 3.)

1. Hane

Hane 1  

Obviously, a hane fails.
Playing W1 at W3 immediately would resolve to the carpenter's square.
Playing W3 at B4 would allow Black to capture W1 and make two eyes.

Hane 2  

The other hane has a continuation like this, which results in a seki or a ko:


2. Vital point

Vital point  

This is the main line: W3 is quite a move. Black cannot make two eyes after W11 at a.

Vital point var  

If Black maximizes his eye space, W7 makes an eye in the belly

3. Simpler way


Panda Sensei shows a different, simpler way to kill.


Simple enough.

L-group on the 4th line last edited by hnishy on January 30, 2023 - 00:34
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