AB=AC,AB⊥AC
网友回答
AC=AB,外加垂直条件得出∠ABC=∠ACB=45°,∠BAC=90°
梯形上下底平行,∠ABC+BAD=180°计算得∠BAD=135°
设AB=AC=1,根据勾股定理得BC=BD=√2
根据正弦定理
AB/sin(∠ADB)=BD/sin(∠BAD)
1/sin(∠ADB)=√2/sin(135°)=√2/（√2/2）=2
得出sin(∠ADB)=0.5查表可得∠ADB=30°梯形上下底平行∠ADB=∠DBC=30°
∠DBC=30°,BC=BD,∠DCB=∠CDB=75°