α = 1/9 * k * 360 (k= 1 or 2)

∴ α = 40 or 80

2. Make an image first, and then get it.

{α α = k * 360+225 or α = k * 360-45, k ∈ z}

3.2α=k*360 +α，k∈z，α∈[0，360]

α = k * 360 (take k=0)

∴α=0

4. The terminal edges of angles α and β are symmetrical about the Y axis,

Then β = k * 360+ 180-α, k ∈ z,

And β+α = k * 360+ 180.

=(2k+ 1)* 180，k∈Z，