Chapter: Geometric Constructions· Mathematics Part 2 (Geometry)
Answer: 100°
In quadrilateral OAPB, the angles at A and B are 90° each, so \(\angle AOB = 360^\circ - 90^\circ - 90^\circ - 80^\circ = 100^\circ\). (\(\angle AOB\) and \(\angle APB\) are supplementary.)