參考影片
https://www.junyiacademy.org/course-compare/math-high/math-11/high-school-triangle/high-school-triangle1-2/v/avyoEYOvZ98?v=avyoEYOvZ98
14 下列何者為正數? (A)cos 240° (B)cot120° (C)s..-阿摩線上測驗