来自葛江华的问题
已知等腰△ABC中,AD⊥BC于点D,且AD=12BC,则△ABC底角的度数为()A.45°B.75°C.45°或15°或75°D.60°
已知等腰△ABC中,AD⊥BC于点D,且AD=12BC,则△ABC底角的度数为()
A.45°
B.75°
C.45°或15°或75°
D.60°
1回答
2020-05-31 10:54
已知等腰△ABC中,AD⊥BC于点D,且AD=12BC,则△ABC底角的度数为()A.45°B.75°C.45°或15°或75°D.60°
已知等腰△ABC中,AD⊥BC于点D,且AD=12BC,则△ABC底角的度数为()
A.45°
B.75°
C.45°或15°或75°
D.60°
①如图1,点A是顶点时,∵AB=AC,AD⊥BC,∴BD=CD,∵AD=12BC,∴AD=BD=CD,在Rt△ABD中,∠B=∠BAD=12(180°-90°)=45°;②如图2,点A是底角顶点,且AD在△ABC外部时,∵AD=12BC,AC=BC,∴AD=12AC,∴∠ACD=30...