The transformation regarding to the mirror reflection to this line L comprises the subsequent basic transformations:
1) Translate the intersection point A(0,c) to the origin, it transfers the line L to L'.
2) Rotate the transferred line L' by -θ degrees hence the line L' aligns along with the x-axis.
3) Mirror reflection regarding to the x-axis.
4) Rotate the x-axis back via θ degrees
5) Translate the origin back or reverse to the intercept point (0,c).