Question

AB是⊙O的直径，点C在圆上，∠ABC=63°，那么∠OCA的度数是________．

Answer

27°

【解析】

根据直径得出∠ACB=90°，进而得出∠CAB=27°，进而解答即可．

∵AB是⊙O的直径，∴∠ACB=90°．

∵∠ABC=63°，∴∠CAB=27°．

∵OA=OC，∴∠OCA=∠CAB=27°．

故答案为：27°．