Capturing Race Exercise 13 / Solution
threatens to make life in the corner, forcing . An extra approach move is necessary to capture giving black time to capture the white stones on the outside.
If white tries to fill inside first with , black captures leaving a 3-space big eye to fill. or at has the same result.
here looks like it does the same thing, but actually invites ko. Black doesn't have time to play at to prevent the ko - that will lose the race outright.
If simply reduces White's liberties, and can turn the corner into a ko.