12) Given angle is 90 degrees. Find angle AOB.

The diagram shows a circle with center O. OA and OB are radii. The angle $$\angle AOB$$ is a central angle. The symbol at O indicates a right angle, meaning $$\angle AOB = 90^\circ$$. The line segment AB is a chord.

The question is asking to find $$\angle AOB$$. From the diagram, it is directly indicated that $$\angle AOB$$ is a right angle.

Therefore, $$\angle AOB = 90^\circ$$.

Ответ: 90°