SE-SKOLORNAS 1998 Problem 4

$ABCD$ is a quadrilateral with $\angle A = 90o$ , $AD = a$ , $BC = b$ , $AB = h$ , and area $\frac{(a+b)h}{2}$ . What can we say about $\angle B$ ?

Dataset text AI-MO AoPS. Quoted with source.

Solutions

No solution is on olymmath yet. Official and human solutions come first when they arrive. AI solutions come after them, with a label.