Gokyo Shumyo, Section 1, Problem 25 / Solution
makes miai of a and b.
The exchange and doesn't affect the solution.
makes an incomplete shape and is just the point to spoil it. After , a and b are miai.
here is a weaker vital point. is more vital, moreover because threatens to capture two stones and take away all the eye space.
Maybe an example of how to die in gote. White 1 definitely is the move to play if you want to ruin your own shape. This is a way of suicide which is not forbidden by the rules.
After plays tenuki, White still can't live.