Xuanxuan Qijing Problem 19 / Solution

Solution  

Note that this solution only works because the marked black stones have no outside liberties ( puts them into atari and black has no time to play at ).

Solution for #1  

If black plays 'a' this is revert to the original problems, and it's wrong. The best black can do is here. More information at long L group; it's alive in seki.

Solution for #2  

here is correct. 'a' would make black alive too, but only in seki; when black plays the group lives with points.

Solution for #3  

In a situation like this the best black can do is get a ko with here. More information at long L group. If you have been looking at this page carefully, it's obvious 'a' doesn't work for black.