4.3. Straight line on a plane

Let the PDK set on the plane. The equation sets a line on a plane and is called the general equation of a line . To write a general equation of a straight line, you need to know the normal vector. (the normal of a line is a straight line perpendicular to this straight line) and one point of a straight line

Where

If you know the general equation of a line, then you can find the normal equation of a line:

Where

The plus sign or minus sign is chosen so that p > 0. Here φ is the angle between the normal vector n and the axis O _x .

If the normal equation of a straight line is known, then it is easy to find the distance ρ from the point to this straight: