A:Happy Teacher's.
B:Teacher's Day.
C:Happy Teachers' Day
D:Happy Day.
一个盒子有1个红球,1个白球,这两个球除颜色外其余都相同,从中随机摸出一个球,记下颜色后放回,再从中随机摸出一个球,则两次都摸出红球的概率为( )
已知函数f(x)=2﹣2cos2(π4+x)﹣3cos2x
(1)求函数f(x)在x∈0,π时的增区间;
(2)求函数f(x)的对称轴;
(3)若方程f(x)﹣k=0在x∈π4,π2上有解,求实数k的取值范围.