how to calculate distance between two lines?
Distance between Two Parallel Lines It is equal to the length of the perpendicular distance from any point to one of the lines. Let N be the point through which the perpendicular or normal is drawn to l1 from M (− c2/m, 0). We know that the distance between two lines is: d =|Ax1 + By1 + C| / (A2 + B2)½.