Tripod Group with Extra Leg
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While the regular tripod group without the exchange is unconditionally alive, the tripod group with the extra leg is unsettled. If White plays first, the result is a ko. This happens because Black has actually one liberty less and is thus not able to live in oshitsubushi (see tripod group, diagram 7 and Comparison with regular tripod group below).
here is inferior, after , a ko is unavoidable. If Black a, then White b; if Black b, then White c. In any case, White takes the ko first.
Here, it is just a transposition back to the previous diagrams.
For the throw-in at , can also take the ko.
For reference, this diagram shows the regular tripod group without the extra Black leg at a and the White blocking stone at b. It is known that this regular tripod group is unconditionally alive, and we shall see that the Black a - White b exchange actually reduced Black's liberties.
Without the Black a - White b exchange, can actually play the oshitsubushi.
Again, without the Black a - White b exchange, can actually play here and live unconditionally.
- Beginner Exercise 83, Beginner Exercise 84, Beginner Exercise 85 and Beginner Exercise 86.
- Gokyo Shumyo, Section 3, Problem 81and GokyoSeimyoVolume3Problem99 for exactly this shape
- Gokyo Shumyo, Section 1, Problem 9 for a related shape