Kyu Exercise 18 / Solution

Tengen 2003 - Game 3 - resignation  

doesn't work. White throws in at and Black ends up with two liberties against White's three. ( at )

If White cuts at b, does work, because White b takes away a liberty.

Anon1?: Question: why not at ? Wouldn't that save the corner, take away a couple points?

Anon2?: If at , captures 4 stones, leaving b and the cut at D9 miai to kill something big.

As for the third question ...

Tengen 2003 - Game 3 - resignation  

If - and a secures White's big group in sente or b captures Black's large group. White is ahead in the game, so securing the group is enough.

If at b - which is good style - White c both threatens to capture the cutting stones or to get ahead in the aforementioned capturing race.