解：y=7sin(3x-π/5)的周期T=2π/3 y=|7sin(3x-π/5)|是由y=7sin(3x-π/5)保留x轴上方图像，将x轴下方图像对称到x轴上方而得，∴y=|7sin(3x-π/5)|的周期T=2×2π/3=4π/3
