∠CAO = ∠CAB = ∠COD = ∠ DOB (common arc)

∠AOC +∠ COD + ∠ DOB = 180

∠AOC+∠COD+∠CAO = 180(∠CAO =∠DOB)

-∠ODP=90 (tangent)

∠ DPA = 90 (sum of APDO internal angles = 360; 360- 180-90=90)