Question

函数f（x）=cos（3x+派/4）cos（3x-派/4）的最小正周期为 求详解

Answer 1

=W=这个问题怎么会分到动漫这里来的呢..话说这个化简下不就好了嘛

f(x) = cos(3x-π/4 + π/2)cos(3x-π/4)

= -sin(3x-π/4)cos(3x-π/4)

= -1/2 * 2 * sin(3x-π/4)cos(3x-π/4)

= -1/2*sin(6x-π/2)

= 1/2*cos(6x)

由此最小正周期是 T=2π/6 = π/3