lckjackie 寫到:These questions are very simple.
You can use sin, cos and tan to solve these questions.
Yes , i totally agree with you. But please see th question clearly .
圖中,BCDEF是一直線,∠ABF=90°,AB=EF=1,BC=3,CD=DE=2,求∠BCA+∠BDA+∠BEA+∠BFA。
依規矩,不准使用三角學或座標。