標題:
circles問題 求解答
發問:
問題內容： http://i.na.cx/Q33L5.png please give me (reasons) 謝謝! !
最佳解答:
圖片參考：https://s.yimg.com/lo/api/res/1.2/01HAAsbPB7gy9Hvf3TDefA--/YXBwaWQ9dHdhbnN3ZXJzO3E9ODU-/https://i.na.cx/Q33L5.png Question 1 ∠BOD = 360° - reflex∠BOD (∠s at a pt.) = 360° - 260° = 100° ∠BAD = 0.5 ∠BOD (∠ at centre twice ∠ at circum.) = 0.5 (100°) = 50° ∠BCD = 0.5 relfex∠BOD (∠ at centre twice ∠ at circum.) = 0.5 (260°) = 130° ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? Question 2 (a) AB is a diameter. (given) ∠ADB = 90° (∠ in semi-circle) ∠BDC = ∠ADC - ∠ADB = 130° - 90° = 40° (b) ∠CAB = ∠CDB (∠ in the same segment) = 40° ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? Question 3 ∠ACB = 180° - ∠BAC - ∠ABC (∠ sum of △ABC) = 180° - 101° - 51° = 28° ∠ADB = ∠ACB (∠ in the same segment) = 28°
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