Then ∠ oba = ∠ d = 60,

∫∠AOB = 90，

∴∠ OAB = 30, AB is the diameter,

∴AB=2OB=4，

According to pythagorean theorem OA=2√3,

∴ Point A (2 √ 3,0)

(2)S cycle O=π( 1/2AB)? =4π

Ask if you have any questions; If you are satisfied, please adopt it. thank you