Endgame Problem 3 / Solution
saves the stones. If Ba instead, may lead to their capture.
And now makes a seki. Black can play a ko but with the risk of losing everything. Hans
Miai Value analysis
Let's take this as the zero diagram.
After , A and B are miai for Black, so he lives with 7 points. C-D is still Black's sente.
Instead of playing the seki, White can also execute - in sente. Later, Black's block will be sente, so we count this as 4 points (5 for Black and 1 White at D).
So this is a sente with value 3, while making the seki is a gote move with miai value 3.5 and therefore better in most circumstances.
White can kill the whole group this way
This might be the strongest resistance: ko.
White can also take 8 stones in sente (the follow up would be larger).
If White takes the sente rather than the ko, we get the following game tree
-6.25 (9.75)
/ \
3.5 (3.5) -16 (0|21))
/ \ / \
7 0 -16 (-37)