自主学习
【例1】
(1)100°
(2)35°
(3)60°
(4)70°
(5)30°
(6)70°
【例2】
∠CAB = ∠DAF - ∠DAC - ∠BAF = 180°- 40° - 80° = 60°,
由AD∥BE,可得∠_EBA = ∠BAF = 80°,
所以∠ABC = ∠EBA - ∠EBC = 80° - 35° = 45°,
在△ABC中,∠ACB = 180° - ∠ABC - ∠BAC = 180° - 45° - 60° = 75°.
所以从C船看A、B两船,视线CA、CB的夹角∠ACB为75°.
互动探究
1、B
2、∵ ∠B = 65°,∠C = 45°,
∴ ∠BAC = 180° - 65° - 45° = 70°.
∵ AE平分∠BAC,∴ ∠BAE = 35°,
∵ AD ⊥ BC,∴ ∠BAD = 25°,
∴ ∠DAE = 35° - 25° = 10°.