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问题 选择题

“a=1”是“函数y=cos2ax－sin2ax的最小正周期为π”的（   ）

A．充分不必要条件

B．必要不充分条件

C．充要条件

D．既非充分条件也不是必要条件

答案

答案：A

本题考查三角变换,两角和与差的三角函数,三角函数的周期,充分条件,必要条件,充要条件的判定>

,最小正周期为

即函数的最小正周期为π;

函数的最小正周期为π

所以是函数的最小正周期为π的充分不必有条件.故选A

连线题

把句子与重读词语所强调的意思用直线连起来。

我知道你会唱歌。　　　　　　你怎么说不会昵？

我知道你会唱歌。　　　　　　别人会不会唱我不知道。

我知道你会唱歌。　　　　　　会不会唱戏我不知道。

我知道你会唱歌。　　　　　　你不要瞒我了。

我知道你会唱歌。　　　　　　别人不知道你会唱歌。
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