1、3
2、75°
3、25
4、C
5、D
6、∵ ∠B = 90°,BC = 2·OB = AB,
∴ ∠A = ∠C = 45°,
∴ BD的度数为90°,D为AB的中点,
∴ OD∥BC,OD ⊥ AB.
7、∵ ∠ACB = 90°,∠BAC = 2∠B,
∴ ∠B = 30°,
∴ △AOC是等边三角形,
∴ ∠AOC = 60°,在Rt△OAP中,
OA = PAtan60° = 6,
∴ AC = 6.
8、(1)连接OC,OC ⊥ l,OC∥AD,
∴ ∠BAC = ∠OCA = ∠DAC = 30°;
(2)连接BF,∠AFB = 90°,
∵ ∠AED = ∠ABF,∠AED = 90°-∠DAE,∠ABF = 90°-∠BAF,
∴ ∠BAF = ∠DAE = 18°