Beginner Exercise 5 / Solution

Sub-page of BeginnerExercise5

This problem assumes that the reader knows how a ko fight works.

Introduction

[Diagram]

Introduction

This shape looks like the twisted four, but it is at the corner. We note that when the group has only one outside liberty at circle, Black can turn the status of this group into a ko. This is similar to bent four in the corner.


Solution

[Diagram]

Solution: Ko for life

B1 occupies one of the middle points in the twisted four. When W2 occupies the other middle point, B3 takes the ko first. The answer is "Ko for life, Black taking first".

[Diagram]

Comment

W4 attempts to set up a oshitsubushi, but this leaves the White group with only one liberty, so B5 simply captures all the White stones.

[Diagram]

When Black wins the ko

If Black wins the ko, he will connect at B1. The White group has only a bent three eye and dies.

[Diagram]

When White wins the ko

If White wins the ko, he will capture at W1, making two eyes and live.

[Diagram]

Variation

If W2 connects the 1-1 stone, which is under atari, White dies in gote with a bent three eye.

[Diagram]

Variation

If W2 here, B3 leaves the White group in a bent three.



Failure

[Diagram]

Failure

B1 occupies the other middle point, but W2 lives.

[Diagram]

Failure

This lives too.



Additional information

[Diagram]

Two external liberties

When White has two outside liberties, he can live without ko.

[Diagram]

Comment

Even if black attacks with B1 and B3...

[Diagram]

Comment

W4 sets up a oshitsubushi. The atari at B5 is too late, W6 captures two Black stones and makes two eyes.



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