The distance from the focus to the collimator is 5, and the parabolic standard equation is solved RT.
The distance from focus to guide line = P / 2 + P / 2 = P = 5.2p = 10
There may be four parabolic equations: x ^ 2 = 10Y, x ^ 2 = - 10Y; y ^ 2 = 10x, y ^ 2 = - 10x