I ran into this on the first pages when I started reading Basic Techniques of Go. It kept me awake last night.
This joseki is available at SL as 3-4, 5-3 enclosure, capping reduction
I played variations on a goban, and this is what kept me awake late
Only reasonable continuation for white I could find was at a.
unkx80: My answers here:
I think Black has no good answer after , , . If saves the two stones, then makes Black a split shape.
If cuts, then Black's corner is gone after . (Black can continue at a, but this would be a two-stage ko that favours White and heavy for Black.)
Sorry, been busy..
Although the black shape is split, I don't feel it's bad. As far as I can read, white gets only a couple of kikashi to make black lose the corner, but white gets only one eye. The only option for white after this is to run into the center from a tight position. Is stealing the corner worth it, even if white does live?
As for diagram 4, I really don't like the way it looks for black.
And as for diagram 2, I really don't for the continuation, but it feels like my kind of move. :)
Slarty: The above is locally a success for white/bad for black, for being split. That kind of result is still dangerous for white though, it's true. Splitting directly with below is much easier, imo.
symplicity: When evaluating the result, also remember that black started with 4 stones here. What would you expect if you took an typical even corner exchange and then gave black four moves in a row? Often it would be worse for white than dia 5.