在半圆中可得∠BCA=90°,∠BAC=30°,AB=2R,
∴AC= 同类题1 江南style 是在去年七月中旬发行,然后风靡全球。Gangnam Style was issued in the middle of July last year, then it ____.
Gangnam Style was issued in the middle of July last year, then it ____.