注意到首先π/2就是一个正周期,这是因为,sin(x + π/2)不管是等于正的cos(x)还是负的cos(x),取完绝对值都等于 |cos(x)|,同理,|cos(x + π/2)| = |sin(x)|,这样,f(x + π/2) = |cos(x)| + |sin(x)| = |sin(x)| + |cos...