A design for a decorative stained-glass window panel is shown below. The design consists of a sector OBC OBC\,OBC of a circle with centre OOO, flanked by two congruent triangles OAB OAB\,OAB and ODCODCODC. The point O O\,O lies on the straight base ADADAD. The points B B\,B and C C\,C lie on the arc of the circle. The side lengths AB AB\,AB and DC DC\,DC are equal, and the angles ∠AOB \angle AOB\,∠AOB and ∠DOC \angle DOC\,∠DOC are equal and acute.
Given that:
Find the radius of the sector, giving your answer in cm\text{cm}cm to 2 decimal places.
Find the size of angle AOBAOBAOB, in radians, to 2 decimal places.
Hence find: the total area of the window panel, giving your answer in cm2\text{cm}^2cm2 to one decimal place.
the total perimeter of the panel, giving your answer in cm\text{cm}cm to one decimal place.