某学生对函数 f ( x )=2 x ·cos x 的性质进行研究,得出如下的结论: ①函数 f ( x )在[-π,0]上单调递增,在[0,π]上单调递减; ②点( ,0)是函数 y = f ( x )图象的一个对称中心; ③函数 y = f ( x )图象关于直线 x =π对称; ④存在常数 M >0,使| f ( x )|≤ M | x |对一切实数 x 均成立. 其中正确的结论是__________ .(填写所有你认为正确结论的序号)
【简答题】Fill in the blanks with the words given below, changing the form if necessary. Fill in each blank with one word only. damage deny public inspect actually location structure claim r...
【简答题】Fill in the blanks with the words given below, changing the form if necessary. damage deny inspect actually location structure claim amount 1. Bees communicate by dancin...