F.5 maths circle(2)

Please Read：


圖片參考：https://s.yimg.com/rk/HA07344914/o/1959641763.jpg


2014-10-14 02:53:50 補充：
方法1的圖片
http://postimg.org/image/6ncbbg9zx/

2014-10-14 03:00:14 補充：
方法2 最後哥4行可以用∠ in the same segment 去取代
即
∠ACD=∠ABD=56° (∠ in the same segment)

題目要求一定要用 ∠ at centre twice angle at circumference
有時你諗到用 ∠ in the same segment
但諗唔到點用 ∠ at centre twice angle at circumference
咁你試下可以將 ∠ in the same segment 轉做 ∠ at centre twice angle at circumference