The previous judgment of a and b is to confirm whether there is an obtuse angle.

Based on this, the answers to these three questions are analyzed.

1)a & lt； B and A are acute angles, and it is not sure whether B is obtuse, so there are two solutions.

2)a & gt； B, A & lt90', so B must be smaller than A, and it is acute, so there is only one solution.

3)B& gt； 90`, a>B, so A must be greater than B, that is, there are two obtuse angles, which cannot form a triangle, so there is no solution.