British Go Journal No. 65. July 1985. Page 30.
The problems to these answers are on page 25a.
BGJ had solutions 2 & 3 exchanged and had Dias 2a & 2b rotated 90 degrees.
Yose Answer 1a ||
Yose Answer 1b |
Black 1 is a surprisingly important tesuji. If Black does nothing, white can play 1-7 in sente in Dia 1b, making 8 points of territory in the corner. But by cutting at 1 in Dia 1a black gets in a sente hane (3) of his own. After 4 White has the privilege of playing E-F, but his corner is two points smaller than before, while Black has two extra points on the side (at 2 and 4 in Dia 1b).
Since black 1-3 in Dia 1a are themselves sente, and prevent sente plays by White, their total value is considered as twice their nominal worth ie 2 x 4 = 8 points!
Yose Answer 2a ||
Yose Answer 2b |
Dia 2b had black 6 shown as black 5, as well as showing white 5.
Black 1 may take some finding but is a clever tesuji. White 2 is more or less forced, and black 3 forces white to play again. The point about this sequence is that is deprives White of his sente endgame sequence in Dia 2b, after which black's corner is three points smaller and white's side is one point larger. Because black 1 prevents this sente sequence in sente it is worth 2 x 4 = 8 points.
Yose Answer 3a ||
Yose Answer 3b |
Black 1 in Dia 3a is the correct move in this very common shape. The best that white can do now is to play 2 and 4. Later 6 and 7 are White's prerogative.
Now compare this result with Dia 3b, where black succumbs to the urge to give atari. White captures at 2 in gote, like Dia 1. But later white can play 4 and black has to give way at 5, allowing white to crawl once more. As a result black loses two extra points of territory at 7 and 9 compared with Dia 3a.
Yose Answer 3c ||
Yose Answer 3d |
If Black tries to resist by countering 4 in Dia 3b with 5' at 6, he runs into a nasty ko as in Dia 3c. This is a "flower-viewing" ko for white ie white gets a lot of pleasure out of it, since he has everything to gain (wrecking black's side) and virtually nothing to lose.
Note that if it were White's move in the initial position see Dia 3d then 1 is also the vital point, leading to the same result as Dia 3b. If White mistakenly starts by pushing out at 2, Black 4 stops him dead, since 5 would be answered by 6 and white cannot connect. White therefore has to go back and capture the two black stones, ending in gote.
Yose Answer 4a |
Black 1 is a tesuji which protects bothe the cutting point at A (Black replies at B), and defends the marked black stone. Black thus saves a point of territory. After white 2 black then plays a throw-in at 3, another tesuji which robs white of a point of territory, since he will later be forced to connect at C.
If you failed to find the answers to these four problems in an actual game, you would have thrown away 8 + 3 + 2 + 2 = 15 points. Now do you see the importance of yose?