Gokyo Shumyo, Section 1, Problem 89 / Attempts

Black to live  

If Black gets a stone here in sente, he will make two eyes at the circled points.

Var 1  

At 4, White must play in the corner to prevent 2 eyes.

Var at 6 in var 1  

Reverts to the solution in Var 1.

Variation at 4 in Var 1  

Both the moves at a or b let Black live.

Var 2  

So, we get White 2 from the "first pattern". If White 4 at 5, Black 5 at 4 lives. White 6 fills at the marked spot. Next, Black squeezes and lives with 11 at a. This I would call the main line.

unkx80: Yes, the main line and the only solution.

Black to live  

Three other candidates: lure out the cutting stone at a, the awkward but not self evident b and playing the marked stone immediately.

Black to live  

unkx80: How about White 2?