挑战习题
1/5单选题
难度:

1.把一副三角板如图甲放置,其中∠ACB=∠DEC=90°,∠A=45°,∠D=30°,斜边AB=6,DC=7,把三角板DCE绕点C顺时针旋转15°得到△D1CE1(如图乙),此时AB与CD1交于点O,则线段AD1的长为(  )
A
B 5
C 4
D
提示1:
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正确答案:Qg==
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