crystalrd
幼苗
共回答了19个问题采纳率：89.5% 举报
∵∠BCE=75°
∴∠DCE = 90°-∠BCE = 15°
∴DE = CD*tan∠DCE = AB·tan15° = (2-√3)AB
∴AE = AD-DE = BC-DE = 2AB-(2-√3)AB = (√3)AB
∴tan∠ABE = AE/AB = √3
可得∠ABE = 60°
∴∠CBE = 90°-∠ABE = 30°
∴∠BEC = 180°-∠CBE-∠BCE = 75°
∴∠BEC=∠BCE
∴BE = BC
1年前
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