tsumego, maeda, elementary #87

[cyclops]

This problem took me too much time. After I solved it I wondered why it was so difficult. Well, to make up for the time spent, I publish it here on L19.

$$Bc Black to play ~7kyu
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , . , . X . . |
$$ | . . . . . . . . . |
$$ | . . , . , O O . . |
$$ | . . . O O X O . . |
$$ | . . , O X X X . . |
$$ | . . . O O X . . . |
$$ | . . . . . . . . . |
$$ +-------------------+

Click Here To Show Diagram Code

[go]$$Bc Black to play ~7kyu
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , . , . X . . |
$$ | . . . . . . . . . |
$$ | . . , . , O O . . |
$$ | . . . O O X O . . |
$$ | . . , O X X X . . |
$$ | . . . O O X . . . |
$$ | . . . . . . . . . |
$$ +-------------------+[/go]

Hidden: Book solution

$$Bc Solution from book
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , . , . B . . |
$$ | . . . . . . . . . |
$$ | . . , . , O O . . |
$$ | . . . O O X O 2 . |
$$ | . . , O X X X . . |
$$ | . . . O O X . 1 . |
$$ | . . . . . . 3 . . |
$$ +-------------------+

Click Here To Show Diagram Code

[go]$$Bc Solution from book
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , . , . B . . |
$$ | . . . . . . . . . |
$$ | . . , . , O O . . |
$$ | . . . O O X O 2 . |
$$ | . . , O X X X . . |
$$ | . . . O O X . 1 . |
$$ | . . . . . . 3 . . |
$$ +-------------------+[/go]

What took me so long was to refute at 3. OC the distant black stone will play it's role.
Hidden: refutation of variation

$$Bc
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , . , . X . . |
$$ | . . . . . . . . . |
$$ | . . , . , O O 4 8 |
$$ | . . . O O X O 3 5 |
$$ | . . , O X X X 9 b |
$$ | . . . O O X . 1 6 |
$$ | . . . . . 7 2 a . |
$$ +-------------------+

Click Here To Show Diagram Code

[go]$$Bc
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , . , . X . . |
$$ | . . . . . . . . . |
$$ | . . , . , O O 4 8 |
$$ | . . . O O X O 3 5 |
$$ | . . , O X X X 9 b |
$$ | . . . O O X . 1 6 |
$$ | . . . . . 7 2 a . |
$$ +-------------------+[/go]

Because of G7 forces .
After the diagram W only can make a gote seki at a. So B lives.
For me it was hard not to play at b.

Hide: Then why doesn't work at J3 in the last diagram?

$$Bc
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , . , . X . . |
$$ | . . . . . . . . . |
$$ | . . , . , O O 4 8 |
$$ | . . . O O X O 3 c |
$$ | . . , O X X X . X |
$$ | . . . O O X . 1 . |
$$ | . . . . . 7 2 6 a |
$$ +-------------------+

Click Here To Show Diagram Code

[go]$$Bc
$$ +-------------------+
$$ | . . . . . . . . . |
$$ | . . . . . . . . . |
$$ | . . , . , . X . . |
$$ | . . . . . . . . . |
$$ | . . , . , O O 4 8 |
$$ | . . . O O X O 3 c |
$$ | . . , O X X X . X |
$$ | . . . O O X . 1 . |
$$ | . . . . . 7 2 6 a |
$$ +-------------------+[/go]

After this diagram w can choose between a and c to make ko. No idea which is better.

edit: added another section. I hope CnP likes it better!

[CnP]

I'm doing this set but that problem was no use for me. I'm also studying All about life and death and that problem is literally a textbook example of how knowledge of L groups speeds up finding the solution apparently. Sadly I remembered it when I came to it in this set so I couldn't test myself on it