Gokyo Shumyo, Section 1, Problem 66 / Solution

Solution 1  

is the traditional solution. After , is the only defense. White can block at a, atari at b, and hane at c in sente.

Variation  

Alternatively, White may immediately play at and thrust at to leave Black with two points. Compared to above, this tradeoff means that a and b are no longer sente for White.

Black Failure at (i)  

If , White can make ko.

Black Failure at (ii)  

is double atari.

Solution 2  

lives with more points by maximizing eyespace at the cost of creating more ko threats for the opponent.

Variation  

Immediate throw-in doesn't work: Black is alive.

Variation  

However, Black must be careful not to capture with .

inferior defense  

After , is inferior; reduces Black territory ( at is met by at a).