Hi,

I came across this tsumego today (white to kill):



I thought I had figured out 2 ways to kill black and went to the solutions. But alas, according to my book one of my solutions is wrong:



White starts a ko with 3 and if black wins, the group is alive. My problem is that I do not see why white should bother to answer 2 by taking the ko.
If white just plays the vital point of the group, black still has to look for a second eye - and all eyes I can find are false ones.



I tried other variations - but all had in common that black is unable to connect // has only one real eye.

Can anyone else find black a second eye?


Thanks

Jörg

PS: I am aware that playing the vital point directly is probably more elegant

looks wrong. Black answers at g18 and lives.

at J19 on the other hand looks like it works.

_________________
Sanity is for the weak.

Ah .. I believed 5 to work because I can build a 3 stones "dead" nakade with H19 in reaction to G18. I didn't see that it won't work in that case. Interesting!

Anyone sees a way to deal with 5 on J19

...

In my opinion, White G19 is the very vital point.

Black dies, whenever White plays it. There will be no Ko.

_________________
The really most difficult Go problem ever: https://igohatsuyoron120.de/index.htm
Igo Hatsuyōron #120 (really solved by KataGo)

You're right! Sorry for not making it clearer in the first post.

The questions is whether White 1 on D19 also kills. It appears as if it does.

True. But White must follow this Hane with G19 as move 3 anyway.

It White captures on the left instead (and never intends to play at G19), it will arise an approach-move Ko.

_________________
The really most difficult Go problem ever: https://igohatsuyoron120.de/index.htm
Igo Hatsuyōron #120 (really solved by KataGo)

G19 sure is more elegant! I was just confused, because the book I study with rules the hane out. According to the book the Ko is the only way after white 2 on e19.

Lesson of the day: Books are not infallible

Perhaps they mixed it up with the following Tsume-Go:

Click Here To Show Diagram Code

[go]$$
$$ ---------------------------------------
$$ | . . . . . . . . . X . . . . . . . . . |
$$ | . . O X . X . X X O . O . . . . . . . |
$$ | . . O O X X X O O . O . . . . . . . . |
$$ | . . . O O O O O . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |[/go]

_________________
The really most difficult Go problem ever: https://igohatsuyoron120.de/index.htm
Igo Hatsuyōron #120 (really solved by KataGo)

that might be it. On the first glance it really looks pretty much the same.

A Hane on the first line often makes the decisive difference.

_________________
The really most difficult Go problem ever: https://igohatsuyoron120.de/index.htm
Igo Hatsuyōron #120 (really solved by KataGo)

but not this one..
IMO g19 kills black same way

_________________
"The more we think we know about
The greater the unknown"
Words by neil peart, music by geddy lee and alex lifeson

Yes, indeed.

However, the incorrect variation (White D19) ends in Ko now, as Gegenzeit's book told him for the problem without the Hane on the right.

_________________
The really most difficult Go problem ever: https://igohatsuyoron120.de/index.htm
Igo Hatsuyōron #120 (really solved by KataGo)