如图,AB是⊙O的直径,点D在AB的延长线上,且BD=OB,点C在⊙O上,∠CAB=30°.求证:DC是⊙O的切线.
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(1)计算:
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(2)分解因式:x
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已知直线y=kx+b经过(-5,1)和点(3,-3),那么k和b的值依次是( )
A.-2,-3
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C.-
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D.1,6
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能判定四边形ABCD是平行四边形的是( )
A.AB∥CD,AD=BC
B.∠A=∠B,∠C=∠D
C.AB=CD,AD=BC
D.AB=AD,CB=CD
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