⑴? The distance from point A to line BC is the length of line segment AC (as shown in figure 1), and the distance from point B to line AC is the length of line segment BC (as shown in figure 2);

⑵AB is the longest;

∫ Of all the line segments between a point outside the connecting line and each point on the line, the vertical line segment is the shortest;

∴ AC < AB (as shown in figure 1), BC < BA (as shown in figure 2).

∴AC or BC < ab