level 1
t = Tan[theta2]^(1/3)
h = (1 - t^2 + t^4)^0.5/(1 + t^2)
ContourPlot[{Sin[2 (ArcCos[y] - theta2)]/2 + x*Sin[ArcCos[y]] == 0,
Sin[2 (ArcCos[-y] - theta2)]/2 - x*Sin[ArcCos[-y]] == 0, x == -h,
x == h}, {x, -1.2, 1.2}, {y, -1, 1},
ContourStyle -> {Blue, Blue, Blue, Blue}, ImageSize -> {600, 500},
Axes -> True, Frame -> False, Ticks -> None]
这样生成的图如下:

想要的效果图见3楼