Gokyo Shumyo, Section 1, Problem 16 / Solution

Main line  

Throwing in at 5 is key to life. (This is an example of oshitsubushi.)

Variation  

If White continues to destroy Black's eyeshape, she runs out of breath after Black 7. Black will have to connect at a later, but still his eyespace is almost filled with a straight four shape, giving life.

Mistake at 5  

After , Black only has one eye around . And a and b are miai for White to prevent the second eye.

Mistake at 3  

As above, makes miai of a and b to destroy the second eye.

Wrong  

After 4, a and b are miai for killing the corner.

Wrong (variation)  

Black will eventually have to connect at a and b, leaving his eye almost filled with three stones, so he dies.

Wrong (ii)  

White 4 makes miai of 5 and 6. White 6 makes miai of a and b.

Wrong (ii)  

Black 1 here obviously makes only ko, and ko is not good enough.