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  (A)偶函數(shù)且它的圖象關(guān)于點(diǎn)(π，0)對(duì)稱(chēng)         (B)偶函數(shù)且它的圖象關(guān)于點(diǎn)(，0)對(duì)稱(chēng)

  (C)奇函數(shù)且它的圖象關(guān)于點(diǎn)(，0)對(duì)稱(chēng)     (D)奇函數(shù)且它的圖象關(guān)于點(diǎn)(π，0)對(duì)稱(chēng)

函數(shù)y＝(x－a)＋(x－b)  （a、b為常數(shù)）的最小值為(    )

   A.  8      B.       C.       D.最小值不存在

(2006天津，8)已知函數(shù)f(x)=asinx－bcosx(a、b為常數(shù)，a≠0，xR)在處取得最小值，則函數(shù)是

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A．偶函數(shù)且它的圖象關(guān)于點(diǎn)(π，0)對(duì)稱(chēng)

B．偶函數(shù)且它的圖象關(guān)于點(diǎn)對(duì)稱(chēng)

C．奇函數(shù)且它的圖象關(guān)于點(diǎn)對(duì)稱(chēng)

D．奇函數(shù)且它的圖象關(guān)于點(diǎn)(π，0)對(duì)稱(chēng)