Mirrors and bisectors in code

A line is three numbers $(a, b, c)$ for $ax + by + c = 0$. In this lab you write the three functions that every problem of this lesson uses, and then the checker tries them on many points.

Your tasks.

1. In distance, return the perpendicular distance from a point to a line.
2. In reflect, return the image of a point in a line, as a pair of numbers.
3. In bisectors, return the two angle bisectors of two lines, each as three numbers $(a, b, c)$.