Endgame Problem 1 / Solution

Solution 1  

Black cuts at , then peeps at . If White answers at , Black plays at and gets a ko. If White answers at or , this variation occurs. Black captures two stones in sente, and White's corner is worth 4 points. is needed, otherwise Black , White a, Black , and White cannot atari at b due to shortage of liberties.

Solution 2  

here is also a solution. White's best move is . After this, White is unconditionally alive, but Black can capture two stones in sente with . Note the tesuji of that reduces White's territory by one point, without it White will defend at and the corner becomes 5 points. is needed for preventing a snapback at a, and the end result is exactly the same as the previous solution: Black reduced White's corner to 4 points.

Solution 3  

Dieter: I believe playing at the vital point right away also helps. Here are the possible continuations:

• Wa - Bd - We - Bc = ko
• Wb - Bd - We - Bc = ko (almost the same sequence)
• Wc - Bd - We - Ba = life for White and Black captures two stones