1.选B
2.cos(wx-π/4)=sin(wx+π/4)
Y=4sin(wx+π/4)sin(wx+π/4)=3
wx+π/4=π/3、或2π/3,W=1
相邻P3,P4距离为π/2,而|P3P5|=π/2
所以W=2