Tsumego From Games 4
This comes from a three-stone game with me (1k EGF) playing White.
The attention is drawn to the upper right corner. The White group is trying to live thus cutting the top center group from the upper right corner. Had I calculated it a bit earlier, I'd have left this as aji. Black can kill this group.
This is a standard shape, the flying saucer shape, and the hane at 1 kills.
My opponent played 1 and 3. If I continued with a, Black b would still have killed me. If White b, then Black c kills. But, there was a tesuji to save the white group.
White 1 threatens the cut at a and at the same time prevents b in the previous diagram.
If Black blocks, he loses some stones at a or b.
If Black connects his marked stone, White first connects, then captures the stones at a or b.
If Black connects, White lives with 5. White 5 at a would be a big mistake, for Black b will make miai of 5 and c to kill.
So Black protected at 2 and White went on to live in the corner with 3. Next, if Black a, White b.